Some of the most innovative power generation installations around the globe

Some of the most innovative power generation installations around the globe

Power generation projects that feel that they merit special attention because of advances in one or more of the following areas: efficiency increase, environmental aesthetics, operation characteristics, emissions improvements or construction principles.

GE helping make ‘Blue Sky’ a reality in China

The battle for blue skies is a priority in China and government at all levels are strictly enforcing laws to ensure control of air pollution.  A smog-busting program like the “Blue Sky” plan aims to quickly cut pollution in China’s largest cities. One of the targets of the plan is nitrogen oxide (NOx), a pollutant emitted by power plants that burn fossil fuels and a contributor to ground level ozone. Reductions in its emissions will help improve air quality and public health.

Shenzhen is a major sub-provincial city located on the east bank of the Pearl River estuary on the central coast of southern Guangdong province. With a vibrant economy, Shenzhen was one of the fastest-growing cities in the world in the 1990s and the 2000s and it is a significant high-tech hub, therefore it’s often defined the “China’s Silicon Valley.”

Once it was also known for spewing out dark clouds of toxic smoke, but now it has done much to clean up and become a more sustainable city in less than six months. Thanks to “Shenzhen Blue Sky” initiative, the area managed to reduce its average air pollution by around 50 per cent, thanks to GE, that helped five power generation enterprises in Shenzhen (Shenzhen Nanshan Power Corporation, Shenzhen New Power Corporation, Shenzhen Datang Baochang Gas Power Generation Co. Ltd., Shenzhen Yuhu Power Co. Ltd., and CNOOC Shenzhen Power Co. Ltd.) meet their goals.

Shenzhen’s power producers faced strict and firm requirements to lower the NOx emissions within the target deadlines set by the authorities, and if they failed to comply with these requirements will be taken offline. GE tackled the root problem in the combustion system of the gas turbines, and modernized nine GE units installed at the plants with a new pre-combustor system called DLN 1.0+ Ultra Low NOx.

“Power generation companies are currently facing dual pressure from environmental indicators and economic performance,” said Liang Jianqiang, Head of Shenzhen Nanshan Power Plant. “We continue to search for a two-way solution to help contribute to local blue skies while improving asset performance. GE’s DLN 1.0+ Ultra Low NOx combustion upgrade is a perfect fit for our needs. Through this cooperation, GE has not only confirmed its technological advantage, but also demonstrated its excellent capabilities in execution. With the help of GE, we have succeeded in upgrading our plants while maintaining a steady supply of energy.”

GE’s Dry Low NOx (DLN) solution dramatically reduces NOx emissions. The previous versions “DLN1” standard, emitted 15 parts per million (ppm) of NOx, but the DLN1+ upgrade, which is receiving its first global application in China, can bring that down to 5 ppm.

“We admire the Shenzhen Municipal Government’s adherence to greener and lower-carbon development and the efforts to improve the living standards of their citizens,” said Yang Dan, CEO of GE Power China. “GE’s DLN1.0+ with Ultra Low NOx reduced emissions and is contributing to the Shenzhen Municipal Government’s ‘Blue Sky’ sustainability plan to improve air quality. The successful modernization of nine gas turbines – in a record time of less than six months – provides a reference for many 9E units to repower and adapt to the needs of the new era”.

The secret behind lowering the gas turbine’s NOx emissions involves reducing the temperature of the flame inside the combustor. A leaner fuel mix, whereby the natural gas burns in a higher volume of air, can deliver this cooler, low-NOx flame. In addition to hardware modifications, the software called Corrected Parameter Control (CPC) gathers mountains of data about the turbine’s environment. This includes ambient humidity and temperature readings, as well as inlet and exhaust pressure, which are all factors that can affect the production of NOx and other pollutants. These inputs are always changing, so the software is constantly correcting the air-fuel mix to deliver lower NOx emissions.

“In addition, from a technological perspective, GE’s DLN1+ ULN solution is much better compared to other solutions available to reduce NOx” said Bruno Monetti, GE Power Product Manager. “Selective Catalytic Reduction (SCR) systems are more expensive and can have negative environmental impact as they are using ammonia and water to remove NOx. Gas turbines equipped with SCRs have reduced efficiency, thus emitting more CO2 than gas turbines with DLN1+ Ultra Low NOx”.

Completed in a record time, less than six months from receiving the request to complete the project, the modernization of the nine GE’s 9E gas turbines mobilized more than 200 experts from China and around the world for factory repairs to meet specific timeframe requirements and exceeded performance expectations.

GE is engineering cleaner, more accessible energy that people depend on, powering growth and prosperity everywhere. This milestone – in terms of execution excellence and innovation – serves as a model for plant operators that are operating more mature gas turbine fleets in China and around the globe.

A modular concept from Jenbacher replaces coal-fired plant

In 2015, Stadtwerke Kiel set out to replace a 50-year-old hard coal-fired cogeneration plant in Kiel, Germany. The project, distinguished by its efficiency and flexibility, is one of its kind in Europe and is future-oriented and exemplary for the successful implementation of the energy transition by using highly efficient and flexible combined heat and power generation. As part of the project, INNIO Jenbacher provided 20 of its Jenbacher J920 FleXtra gas engines, which went online in December 2019.

The new plant has an electrical output of 190 MW and has a thermal output of 192 MW. Power and heat from the power plant are fed into the electricity grid and district heating network operated by utility provider Stadtwerke Kiel and thus play a major part in maintaining grid stability in North Germany.

The power plant’s modular generation concept allows the facility to respond to changing demand in the energy market with a high degree of flexibility. Each of the 20 Jenbacher gas engines can be ramped up to full load—its maximum generating output—in less than five minutes. This capability means that the power plant can react flexibly to variations in the grid at all times and makes it an excellent counterbalance to the copious yet volatile wind and solar energy resources in this region.

The overall efficiency of the installed INNIO Jenbacher systems is above 92%. The coastal power plant started commercial operations just in time for the 2019/2020 heating season and hereafter will make a significant contribution toward Germany achieving its aim of phasing out coal-fired plants by 2038.

INNIO and KAM engineered and implemented the coastal power plant. While INNIO provided the gas engines and engineering expertise, KAM operated as the general contractor responsible for engineering, procurement, construction and commissioning the turnkey power plant, including the auxiliary buildings and integrating the heat storage and electrode boiler. The team arranged the power plant in four units of five blocks each, with the advantage of being operable in slices.

The large-scale turnkey facility replaces a coal-fired power plant on Kiel Fjord that had been generating electricity and heat since 1970. The high overall efficiency of more than 92% will enable Stadtwerke Kiel to reduce its carbon dioxide emissions by around 70% compared to the previous coal-fired power plant. As a result, the city of Kiel is on track to achieve its climate change goals as early as 2020.

“We are proud that our flexible, highly efficient and advanced gas engine solution will make a significant contribution to this lighthouse project by Stadtwerke Kiel. With Germany’s plans to shut down all coal plants and rely primarily on renewable energy, our Jenbacher J920 gas engines will help balance the Kiel grid,” said Carlos Lange, [resident and CEO of INNIO. “As renewable energy usage will continue to grow across Germany, INNIO will continue to make significant investments in research and development and will further expand its technological leadership in power generation based on regenerative gases-in specific, hydrogen and hydrogen carrier gases-to help build out 100% carbon neutral and carbon free power plants.”

Peak power in two minutes: Wärtsilä’s flexible generation solution

Centrica, an international energy services and solutions company, has recently completed the biggest medium-speed peaking power plant in the country, at its existing site in Brigg in North East Lincolnshire. The peaking plant comprises 5 x Wärtsilä 34SG engines, running on natural gas and delivering a total capacity of 50 MW, enough to provide electricity for almost 100,000 homes.

The background to this story is the changing energy landscape in the UK, with the country increasingly turning to renewable and low carbon sources of energy for its electricity generation, while old baseload plants close across the country. This development has been driven by government policies and advances in technology.

The government in the UK is working towards closing all the UK’s remaining coal power stations by 2025. While the future definitely looks green, the big question on everyone’s mind is how to maintain flexibility and reliability of power generation. Incorporating more renewable sources into the grid, as the country is intent on doing, requires having back-up generation for when the sun doesn’t shine or the wind doesn’t blow. One solution is hybrid power solution systems.

Centrica is among those leading the charge on this front, buying two 50 MW power plants from Wärtsilä, one for the new plant at Brigg and another for a new unit at Peterborough, to provide balancing power to the UK national grid.

“This will help us accommodate an increasing share of renewable energy in our power mix while ensuring that supply remains stable,” says Alan Barlow, UK & Ireland Distributed Energy Director at Centrica Business Solutions, which provides energy expertise and distributed energy solutions to organizations around the world.

“The ramp-up time was a critical factor in us choosing these engines, which will together be capable of providing electricity in just two minutes from start to full load.”

Wärtsilä supplied the engines on an EPC (engineering, procurement and construction) basis to Centrica and were the only company able to provide this very quick start-up time. Achieving this, by paying attention to preheating and pre-lubrication systems, was the key factor in Centrica’s decision to opt for Wärtsilä’s solution.

This speed and flexibility is critical as it allows utility companies to switch over to the supporting generators when renewable energy sources falter. It helps optimize the energy system well in advance, thus keeping the energy grid stable.

“The two-minute start-up time that Wärtsilä’s solutions deliver is a rare feature and very important to the UK grid,” Mr. Futyan said.

When looking for partners for the Brigg project, the company wanted to find someone with a solid track record of delivering quality products safely. Wärtsilä, in Futyan’s words, ticked all the boxes.

The sites at Brigg and Peterborough play a critical role in supplying peak demand to the national grid. This is backed up by a long-term service agreement (LTSA) between Wärtsilä and Centrica. The six-year agreement ensures Centrica has access to 24/7 emergency support from Wärtsilä’s Expertise Centre in Vaasa, Finland.

Bent Iversen, Senior Business Development Manager at Wärtsilä Energy Business, said: “The UK is the leading country in shaping the electricity markets and Centrica is one of its leading operators. Today, renewable power sources provide roughly a third of the country’s total generation capacity, compared to five percent in 2006, and the share is increasing all the time. To support this trend, fast-starting, flexible generation is essential.”

The new power station at Brigg, specially adapted to Centrica’s requirements, is based on Wärtsilä’s modular internal combustion engine (ICE) units. The unique operational flexibility of the ICE technology, with ultra-fast starts and stops and quick loading, ensures seamless control over load fluctuations. As energy demand grows, the modular design makes it easy to expand the power plant to meet any future needs. Plants can be upgraded at any time without risking operational reliability.

While the UK market will be looking to energy storage solutions and sophisticated energy management systems to improve its capacity to react to fluctuations in peak energy supply, Jan Andersson, Senior Market Development Analyst at Wärtsilä Energy Business, sees a continued role for gas. The country will increase its gas capacity to supplement the remaining nuclear and coal plants when renewable generation is low.

“The focus is on renewables, but gas will be used to bring needed flexibility to the system,” he explained.

MAN Energy Solutions delivers CHP power plant in Stuttgart

MAN Energy Solutions handed over a new solution for combined heat and power generation (CHP) to German energy company, EnBW (Energie Baden-Württemberg AG), in early 2019. The 30 MW HKW3 plant lies in the Gaisburg district of Stuttgart, Germany with three MAN 20V35/44G gas engines at its heart, producing 31.2 MW of electrical power for the local grid and up to 30 MW of district heating simultaneously, while operating at a total efficiency of up to 90%.

The new engines are part of an extensive modernization program for the HKW3 cogeneration unit. In addition to the CHP plant, EnBW, has also constructed a heat storage and a boiler plant with up to 175 MW thermal energy output to cover fluctuations in supply and demand.

The new facility replaces a coal power plant – after 60 years of operation – and is projected to save up to 60000 metric tons of CO2 annually. Its new chimneys are half the height of the old ones, and the entire plant is also smaller than its predecessor, although both efficiency and output have both increased.

The main advantage of the entire solution is flexibility. The CHP plant is a core element of the modular concept of the new construction: while the gas boilers exclusively produce heat and are primarily designed to cover peaks in demand over winter, the gas engines are ideally run continuously to provide both electricity and heat. By combining the facility with a district heating accumulator, EnBW can fully exploit the flexibility offered by the engines and react to price signals. When demand for heat is low, the waste heat from the engines can be stored. The high reaction-speed of the MAN gas engines facilitates this flexibility with the units capable of reaching their full output in less than five minutes, while handling load changes effortlessly.

The plants engines can be turned off in less than three minutes, and ramped back up to full load within three minutes in contrast to other, similarly-sized power plants that typically have much longer startup times, the company said. MAN Energy Solutions’ global after-sales brand, MAN PrimeServ, will handle the engine’s service and maintenance for 10 years.

“Large gas engine power plants are a new but important technology in Germany: They help to reduce harmful emissions and guarantee an extremely reliable supply,” said Dr. Tilman Tütken, vice president and European sales manager for MAN Energy Solutions’ Power Plant division. “Gas engine power plants have the potential to replace coal power stations in a way that is not only effective but better for the environment. Our modular power plant concept for cogeneration […] works on the modular principle and can be scaled up as required from 7 MW.”

Jens Rathert, Project Manager at EnBW said the reconstruction of HKW3 enables the company to significantly reduce emissions of CO2 and other pollutants, which is particularly important given the urban surroundings of the power plant.

“Looking at the bigger picture of the energy transition, we regard facilities like HKW3 as a blueprint for further fuel-switch projects and relish the opportunity for more projects along these lines,” Rathert said.

Indeed, the partly state-owned energy supplier’s plans align perfectly with Germany’s climate goals as a whole. According to a recent study, replacing coal with gas plants across Germany could save around 70 million metric tons of CO2 annually, amounting to 40% of the reduction target set by the country’s long-term climate strategy.

Siemens helping energize Bolivia

About 10 years ago, Bolivia had one of the lowest electrification rates in Latin America: Only half of the rural population had access to electricity. An ambitious Siemens project is helping turn this situation around by making an enormous contribution to the provision of universal electricity coverage in the country by the year 2025.

This huge task – known by the project name Energizing Bolivia – resulted in 1 GW being added to the national grid back when Bolivia’s power production in 2015 was only about 2 GW in total.

In the initial phase from 2007 to 2015, Siemens supplied 13 gas turbines for three new-build power plants owned and operated by the state-owned power generation utility Ende Andina SAM in three different regions of the country. Nine SGT-800 gas turbines were provided to the power plants in Warnes and Del Sur, while four SGT-700 gas turbines were supplied to another plant in Entre Rios. Running in simple cycle mode, the three power plants were the primary cause of the doubling of total power generation in Bolivia between 2007 and 2016. The Siemens project then proceeded to the expansion phase by initiating upgrades to the country’s three largest power plants.

In an effort that became a master class in logistics, 14 more SGT-800 gas turbines, 11 SGT-400 steam turbines with condensers, 22 steam generators, 25 electric generators, 25 transformers, and the SPPA-T3000 instrumentation and control system were shipped to the three plant sites between May 2017 and August 2018. Beginning on three different continents, this global effort traversed thousands of miles. Up to 400 heavy-load transports crossed the Andes to bring equipment to the three power plant construction sites, overcoming a 4680 m. elevation change, passing over specially modified bridges and covering a distance of 1800 km. in constantly changing and often extreme weather conditions and rugged topography. Due to their location in very different regions of the country with diverse climatic conditions, the engineers had to devise customized methods of cooling appropriate for rainforests, scrub woodland, and tropical savanna. During construction, up to 1700 workers were deployed across the three sites. It was worth the effort, because in combined cycle mode the three plants’ efficiency was increased from 40 to 51%.

Inauguration ceremonies for the three power plants were held in August and September of 2019. The newly installed turbines were a decisive factor in the huge 1 GW increase in the power plants’ performance, boosting both output and efficiency. The 14 state-of-the-art SGT-800 turbines have a power output up to 53 MW each and a turbine speed of 6608 rpm. The 11 SST-400 steam turbines provide a power output up to 47 MW each at a turbine speed of 5146 rpm.

Thanks to Energizing Bolivia, the country is on its way to energy independence. Bolivia is also looking to become a regional power hub by achieving the goal of increasing generating capacity to 6000 MW by 2025, 3000 of which will be designated for export. “The process of converting gas into energy is now more efficient, the country has the opportunity to find a use for surplus or residual amounts of gas that will be produced as a result of the integration of the new, much more efficient Siemens technologies,” said Ramiro Becerra Flores, project director at ENDE Andina. “It’s going to make the interconnected system highly reliable, and the availability of electricity means we will have the tools to facilitate the general socio-economic development of the country, thanks to the availability of a service and a resource such as electricity.”

By playing an active role in the economic and social development of Bolivia, the project exemplifies Siemens’ Business to Society approach. The company is also committing to the region with a new Service and Training Center in Warnes, where Bolivian technicians will be trained to maintain, monitor, and repair power plant turbines and other components. The center will serve as catalyst for maintaining and optimizing power plant performance in Bolivia and throughout Latin America. The country has embarked on a path that will enable the production and export of value-added products and the development of human capital – which in turn will lead to an improved standard of living for its citizens.

Mining power from Solar Turbines

Genser Energy is an independent power producer headquartered in the USA with operations across West Africa. Genser’s largest operation is located just outside the town of Tarkwa in the jungles of southern Ghana. The Tarkwa Plant is on the mining concession of the Golf Fields Ltd. Tarkwa gold mine in the West African jungle.

In this region, the majority of power is provided from hydroelectric and thermal sources. However, the energy industry in Ghana is constantly evolving, including the type of power being produced and the method to produce it.

Genser energy’s vision is to increase generation capacity in Ghana and West Africa by providing sustainable and cost-effective solutions to the gold mines as well as the people in nearby villages.

Genser previously purchased three Mars 100 generator sets I the secondary market. Pleased with the operation of the equipment, Genser decided to purchase an additional unit to provide the power required by the mine. However, upon searching the secondary market independently as well as leveraging Solar’s knowledge of available equipment, suitable equipment was simply not available without extensive modifications. As a result, Genser elected to purchase Solar’s new PGM130 powered by the Titan 130 to add to its power plant. For more than three years, Genser has operated the three Mars 100s as well as the new PGM130 on vaporized propane. Genser delivers the fuel via truck daily from the Takoradi port, enabling the plant to operate around the clock. Genser also understands the needs of its customers and invested and built a natural gas pipeline to permanently secure the fuel supply and ensure their success.

The Tarkwa power plant currently produces 48 MWe of power. Genser Energy is currently in the process of upgrading the Tarkwa Plant from simple cycle to combined cycle with the addition of one PGM130 and a steam turbine to increase capacity to 91 MWe.

Siemens engines address ever-challenging customer needs

Sensation is an innovative greenhouse in the Netherlands and considered a leader in flower quality and consistency. The company is well known for a certain breed of flower called the Pina Colada, bright white in color, reminiscent of the cool drink on a hot summer day.

Located in Tuil, Netherlands, Sensation required an upgrade of their combined heat and power systems existing of two 1 MW engines, to increase efficiency, with integrated CO₂ recovery for fertilization into the existing footprint.

The CO₂ generation had to be taken into account for fertilizing of the plants while also ensuring climate temperature control needed to maintain the quality and consistency of each flower. Finally, the customer also wanted the ability to operate in a microgrid mode if needed.

Sensation turned to Siemens and its local Dutch Partner Dordtech for expertise and the SGE42-HM was determined to be the right solution to meet all requirements. Siemens said the H Series engines represent a new concept in engine design with advanced technology incorporated into the cylinder heads, valves, camshafts, and turbochargers.

This enabled the customer to run 1 MW of power in a microgrid configuration using a combined heat and power system with only a slight elevation in water temperatures, ensuring all environmental requirements were being met. Two SGE42-HMs engines,

combined with a tailor-made heat exchange and control system designed and fabricated by Dordtech, were designed to operate in a microgrid configuration. The engines were also connected and actively integrated into the Dordtech exhaust gas cleaning system to deliver optimal power efficiency and CO₂ levels for the plants.

Through this partnership, Siemens advised Sensation that the gas utilization for a 2 MW output with 2 SGE-42 HMs would achieve an efficiency of approximately 42%, savings of close to 10% on gas consumption compared to its existing system. In the first four months of operation, actual performance values indicated an increase in efficiency to 44%, with a calculated LHV of 8.61kWh/Nm₃ measured over intervals containing an 80% power demand. Even with the challenges of interconnecting systems and still having the ability to operate as a microgrid, the SGE42-HM demonstrated its ability as the right solution for our customer to maintain

Sensation’s innovative position in the market, while ensuring reliability, efficiency and cost optimization. One of the most admirable features of the SGE42-HM is the ability of the system to be easily modified into different configurations in terms of hardware, to offer the flexibility of integration into other system types.

This flexibility along with the guarantee of a 42% increase in efficiency for the plant, made this partnership a technically innovative journey to ensure Sensation operates one of the most technologically advanced greenhouses on the market.

The customer valued Siemens’ expertise, professionalism, and technical knowledge along with delivering on its guarantees, make Siemens a key solution provider and leader in the energy industry.

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High Energy Users Opting for Combined Heat and Power

High Energy Users Opting for Combined Heat and Power

High Energy Users Opting for Combined Heat and Power

Industrial high energy consumers are increasingly opting for the deployment of combined heat and power CHP technology in the United Kingdom.

With increasing energy prices resulting from hikes in electricity generation and transmission costs, the United Kingdom is seeing growing numbers of manufacturing and production facilities opting for self-generation of power with the deployment of CHP technology. Key industrial sectors with high power consumption includes food and drink processing, the automotive sector, pharmaceuticals, chemicals and metals processing.

CHP plants are captive power plants that generate electricity, typically from gas, and in-turn recover heat from the generators, either as hot water or steam for local use. Generating power close to the site of use not only reduces losses associated with the transmission of electricity, but also improves total fuel efficiency to around 90%.

Industry Following Early CHP developments in Scotland and Northern England

In the public sector, universities and hospitals have utilised gas engine CHP technology for decades now. Early installations include Dundee University and the Freeman Hospital in Newcastle. Both of these institutions deployed Jenbacher gas engines over 15 years ago to reduce their fuel consumption. Both have now refurbished the facilities using the latest engine models with even higher efficiency levels. Early district energy schemes were also deployed in cities such as Aberdeen, the colder climate making them prime locations for efficient use of electricity and heat.

Key to successful industrial CHP schemes

The key to the success of CHP installations is firstly matching the site’s electricity and heating needs to an appropriate generator and heat recovery system. This is done through a detailed technical evaluation of the half hourly energy consumption data, if available. A decision can then be made upon whether hot water or steam would best meet the site’s heating requirements. If the site has a cooling requirement it is also possible to fit an absorption chiller to support refrigeration or air conditioning systems.

The next consideration is the machinery and systems that supports the performance of the core generator. If either the generator or ‘balance of plant’ are inappropriate for the application then operational problems may occur in the future. The final consideration for the success of a CHP installation is the aftersales support. Much like a car engine, CHP engines have scheduled maintenance. For a machine that runs for almost the entire year, it is important to conduct these as per manufacturer’s guidelines and supported by highly trained and equipped service engineers, such as those provided by gas engine specialist Clarke Energy.

CHP evolution

Recent years have seen a much wider deployment of CHP technology for a range of new applications. Rising fuel costs and a starker ‘spark-spread’ – the difference in the price of electricity and gas – along with a focus on reducing carbon emissions are all important drivers.

London in particular has seen massive growth in CHP technology over recent years. A range of high profile buildings now utilise gas engines for cogeneration including the National Gallery, the Shard, and the Natural History Museum. Deploying the technology supports the cost and carbon reduction drive and is also looked on favourably by planning departments from a sustainability perspective.

District energy in the capital now forms the back-bone of many large new commercial developments. The King’s Cross scheme has two bright pink Jenbacher engines supporting a large district heating scheme supplying commercial and residential properties alike. The engines being painted pink to raise awareness of breast cancer research. The redevelopment of the area around Victoria railway station ‘Nova Victoria’ scheme also is using CHP to reduce fuel costs and carbon emissions.

Hospitals too in London continue to adopt CHP technology with Guys, St Thomas’, Great Ormond Street and Bart’s all utilising the technology as a core to their approach to energy usage. The operational cost focus therefore can be on saving on energy and deploying more resources for patient treatment.

Datacentres are an emerging market for CHP technology. The focus here is on combined cooling and power rather than combined heat and power. Citibank’s datacentre in London is one of the first in the UK to use the technology and can generate 71% of the datacentre’s electricity.

Finally, with the reduction in price of renewable energy technologies such as wind and solar energy along with storage technologies such as batteries, it is possible to integrate these different elements into a microgrid and make an industrial user self-sufficient and minimise carbon emissions.


High energy users can move to an off-grid power generation solution using CHP, possibly integrated with other forms of low carbon power. This provides not only reduced operational costs, but also security of power supply, resilience and significant reductions in carbon emissions.

For more information or to request a free energy audit please contact, or Clarke Energy’s sales team on +44 151 546 4446.

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Anaerobic Digestion (AD) A Renewable Energy Technology

Anaerobic Digestion (AD) A Renewable Energy Technology

Anaerobic Digestion (AD) Reducing Green House Gas (GHG)

Anaerobic digestion (AD) is a process that has been used very successfully in a large number of countries.  Over many years and for a number of purposes. This includes; energy production, nutrient management, waste stabilisation, and pathogen reduction. In all of these uses, it also contributes towards reducing greenhouse gas emissions, both directly and by offset.

It is the only technology currently in the market place that meets the European criteria for second generation bio-fuel production. And can achieve this using a range of mixed wastes, not just purpose-grown biomass. It is also a technology that has been neglected by successive governments. Many of which have climbed on the bandwagons of hydrogen, ethanol and bio-diesel as the renewable bio-fuels of the future. Despite the fact that bio-gas plants using the same substrates give consistently higher net energy yields

Investment in Large Processing Plants

AD will certainly make money for those who invest in large centralised processing plants that accept high energy-value waste inputs. Also charge gate fees, and receive subsidy for the heat or power they produce.

This is not, however, a solution that will maximise the energy potential of the available waste biomass. As by far the largest tonnages of materials are animal slurries and manures produced on farms. Although the energy potential of these per tonne is low. Should they be digested on farms, the overall net energy yield is significant

An even greater benefit may be the fact that digestion can reduce greenhouse gas emissions associated with manure management and improve nutrient management on the farm.

What is Anaerobic Digestion?

Anaerobic digestion (AD) is the controlled natural breakdown of organic materials into methane, carbon dioxide gas and fertiliser.  This takes place naturally or in an anaerobic digester.

AD produces bio-gas, a methane-rich gas that can be used as a fuel and digestate, a source of nutrients that can be used as a fertiliser. Increasingly AD is being used to make the most of our waste by turning it into renewable energy.

How Does the Anaerobic Digestion Process Work?

The process takes place inside an anaerobic digester; a large, sealed tank which is void of oxygen. The air supply is restricted to stimulate ‘anaerobic’ decomposition (as opposed to composting, which takes place in the presence of air). After 20 to 60 days, depending on the configuration and internal temperature of the digester, a methane-rich ‘bio-gas’ is produced.

This gas is commonly used for electricity and heat generation, and may also be upgraded for other applications. The biomass is heated to around the temperature of blood, when it will react with the naturally occurring micro-organisms and bacteria. It goes through four stages

  • Hydrolysis
  • Acidogenesis
  • Acetogenesus
  • Methanogenesis

The end result is that the bio-gas is emitted and a residual co-product is an odour-free ‘digestate’, which is rich in plant-available N, P and K and may be directly spread on the land as a fertiliser. Alternatively, digestate may be further separated or “dewatered” into a solid fraction (typically 25-35% dry matter, enriched in P) which can be used as a soil improver, and a liquid biofertiliser containing much of the ammonium and potassium that can be pumped or transported for land-spreading.

Both the gas and the digestate material can be re-used, therefore making it a very effective way to recycle your waste materials.

Anaerobic Digestion a Renewable Energy Technology

Anaerobic Digestion (AD) is one of a number of renewable energy technologies that have become commercially available to agriculture and industrial sectors.  A key attribute of AD is that it offers multiple environmental and economic benefits, particularly for UK dairy and livestock farms.

Anaerobic Digestion Plants Delivering Low Carbon Energy

Alongside their potential to deliver low carbon energy, on-farm AD plants also appear to be the most promising mitigation measure for reducing greenhouse gas emissions from manures and slurries.

Anaerobic digestion isn’t just some new fad though – this technology has actually been around since the 1800s for the treatment of sewage sludge. But, as concerns about the environment grow, so has the demand for ways to generate renewable energy and, as a result, more and more businesses have been investing in AD over the past few years.

The development of AD in Britain has been relatively slow compared to other renewable energy options, with about 125 plants operational at the end of 2013 and 500 by the autumn of 2017. At Powersystems we estimate 650 plants as of April 2019.

Feed-In Tariff (FIT) to April 2019

Up until April this year, the primary incentive available to farmers was the Feed-In Tariff (FIT), based on the installation of an AD plant if UK farmers were to change the way they handle slurry. The FIT, administered by DECC, did not encourage farmers to reduce pollution, but rather paid for them to generate renewable electricity using a combined heat and power plant (CHP) which runs off bio-gas from the AD process.

Powersystems Supporting Anaerobic Digestion and Combined Heat and Power Projects to Create Electricity

However, combining Anaerobic Digestion with Combined Heat and Power (CHP) to create electricity currently has a number of appreciable difficulties if compared with direct gas use (e.g. in a boiler). These include grid connection issues, significant extra capital/maintenance costs and plant complexity in terms of engineering a system which can continuously produce sufficient quantities of quality gas.

Powersystems can illustrate some of the benefits from on-farm AD  with a number of cases studies which highlight the experience of farmers that we have worked with and how we have helped them to overcome infrastructure challenges.

Read this case study about the Farleigh Wallop AD Plant

Challenges of Slurry Utilisation

The average farmer’s options to fully and economically utilise their slurries in an environmentally friendly manner are further compromised by the fact that:

  • the primary feed-stock (cattle slurry) is generally only available for 6 – 7 months when cows are housed indoors over the winter months
  • sufficient year-round on-farm organic substrates may be limited
  • there are significant regulatory financial penalties imposed for digesting the off-farm substrates (which have to be returned to land, anyway), including those which can be fed to cows

 Barriers to Anaerobic Digestion

Some farmers may not have the option or desire to grow energy crops in order to boost bio-gas output to improve the economics of using AD with CHP, for what is primarily their slurry treatment system, especially if the cost of bought in feed increases in line with fossil fuel costs, putting further pressure on farmers to grow their own crops to feed their cattle.

A further barrier is access to capital. Pollution control and other capital grants have largely been phased out. Banks are not prepared to lend money for a technology with which they are largely unfamiliar and suspicious of.

In addition, the UK AD market has been slow to develop (compared to elsewhere in the EU), so technology suppliers of smaller plant, where margins are smaller, tend not to have a large working capital base themselves, further increasing investment wariness.

Turning Waste Into Renewable Energy

Anaerobic digesters generate significant amounts of energy from agriculture materials and waste products from the food chain. The Coalition Government identified development of Anaerobic Digestion (AD) as an early win in 2010 with a commitment to work towards a ‘zero waste economy’.

Anaerobic Digestion can play an important role as a means of dealing with organic waste and avoiding, by more efficient capture and treatment, the greenhouse gas (GHG) emissions that are associated with its disposal to landfill.

AD also offers other benefits, such as recovering energy and producing valuable biofertilisers. The bio-gas can be used to generate heat and electricity, converted into bio-fuels or cleaned and injected into the gas grid.

Bio Gas

Anaerobic Digestion can be applied to a range of natural biodegradable materials, including food waste, slurry, sewage sludge and manure.

  • This material, known as biomass, is naturally broken down until it emits a new gas – known as bio-gas. Bio-gas is a methane-rich gas, comprising of around 60 per cent methane and 40 per cent carbon dioxide. This gas can then be used to generate energy.
  • Bio-gas can be used directly in engines for Combined Heat and Power (CHP), burned to produce heat, or can be cleaned and used in the same way as natural gas or as a vehicle fuel.
  • Bio gas can be used in stationery engines to generate electricity.
  • After removing the carbon dioxide (and other trace gases using a variety of methods in a process known as upgrading) the remaining methane is known as Renewable Natural Gas or Biomethane.

How the AD process works for Food Waste

Anaerobic digestion is an alternative way of composting food waste, while also producing renewable energy and avoiding carbon emissions. The process is called anaerobic because it takes place in the absence of oxygen in a sealed tank. Like composting, it is a natural process dependent on the micro-organisms that digest organic waste.

  • Collection – Food waste, collected from homes and businesses, is delivered – either directly or via a waste transfer station – to the reception hall of an anaerobic digestion facility.
  • Pre-treatment – First the food waste must be pre-treated to remove contaminants such as packaging and it is also diluted with water. Heating this waste mixture to 70°C for one hour kills all pathogens in the food.
  • Digestion – Now pasteurised, the waste is fed into the anaerobic digester. As with composting, bacteria break down the waste, converting it into biogas and a residue, which is called digestate.
  • Energy – Gas piped from the digester is used to generate electricity and heat.

The great thing about food waste is that it is produced by a community, it’s converted to electricity and it goes back to community again – it’s self-sustaining.


  • Is virtually identical to natural gas, the main difference is that is produced in days, rather than taking millions of years, billions of years ago.
  • The uses for Biomethane are therefore as varied as are those for natural gas, for heating, cooling as a source of chemicals, fertiliser or hydrogen.
  • When used as vehicle fuel, bio methane is without doubt, the world’s cleanest and most environmentally friendly fuel.

Carbon Dioxide

  • Is valued for its properties as an inert gas, for heat transfer and as a solvent.

Feedstock Suitable For use in the AD process can include

  • animal manures and slurries
  • energy crops such as maize or rye-grass silage and fodder beet
  • food processing by-products and pack-house residues
  • food waste from retailers
  • biodegradable household waste

What Are The Benefits?

AD provides many businesses with a way to turn the waste products they inevitable produce into new, clean energy, which can then be used on their own site. It can be utilised by any industry which produces food or sewage waste, including agricultural, sewage and food processing, and there are different sized systems available dependent on the amount of waste produced.

The methane-rich biogas which is generated can be used as a source of renewable energy to power electricity generators and provide heat. It can even be altered further and upgraded to filter out the majority of the carbon dioxide – the end result is bio-methane, which can then be used as vehicle fuel or to provide gas. Plus, the digestate can be used as fertiliser, suitable for organic farming systems.

By utilising anaerobic digestion, you can help reduce the amount of waste which you are sending to landfill. This in turn helps to reduce harmful emissions of harmful greenhouse gases, as biodegradable material which is simply sent to landfill will emit a large amount of methane, and carbon dioxide if it is simply left to rot.

How Widely Used Is This Technique?

The spotlight has fallen on waste over recent years. Currently, England generates around 177 million tonnes of waste a year – a disproportionate amount to what is reused or recycled. The government are trying to put measures in place to move towards a zero waste economy, which means that waste resources are fully valued and everything that can be reused and recycled is.

As part of this, the UK government and the European Union Directive have begun to introduce legal and financial incentives for diverting waste away from landfill, so taking advantage of this technology could even bring financial benefits for your business too.

Additionally, more people are looking to businesses to set an example when it comes to waste management and energy use. By utilising a technology which uses waste to create clean energy, you can help enhance your business’s reputation and values, reflecting your business as a responsible, conscientious company.

By investing in anaerobic digestion for your business, you will be taking a step towards making your business greener, and helping the country meet its waste disposal and energy targets

What does the UK produce that can be used in AD plant process?

The UK produces over 100 million tonnes of organic material that is suitable for treatment by AD. This includes:

  • 90-100 million tonnes of agricultural by-products like manure and slurry
  • 16-18 million tonnes of food waste (from households and industry)
  • 7 million tonnes of dry sewage sludge.

 How much energy can you get from waste?

The amount of energy produced by AD will vary depending on the material that goes into it and the particular type of digester that is used. Digesting 1 tonne of food waste can generate about 300 kWh of energy; slurry is lower yielding and purpose grown crops higher. According to the Renewable Energy Association, if all the UK’s domestic food waste was processed by AD, it would generate enough electricity for 350 000 households.

How much energy could anaerobic digestion generate in the UK?

AD could generate 10-20 TWh of heat and power per year by 2020. To put this in context, the UK’s largest power station Drax sold 27.1 TWh of electricity in 2012. AD could represent 3.8-7.5% of the renewable energy we estimate will be required in 2020.

 How many anaerobic digestion plants are there in the UK? 

AD has been used for many years in the UK by the water industry. It currently treats 66% of the UK’s sewage sludge in AD plants. Beyond the water industry AD in the UK is in its infancy, but growing rapidly. There are currently around 100 non-water industry anaerobic digesters in the UK producing bioenergy. You can see the locations of operational AD plants on the Biogas Map. There are many more digesters that are currently in the ‘planning’ stage of development.

Is digestate the same as compost? 

No. Digestate is not compost, although they have some similar properties.  Compost is produced by aerobic (with air) decomposition of biological material and digestate is produced by anaerobic (without air) decomposition of biological material. They can both be used as fertiliser under specific regulations.

 Does AD smell? 

There is some odour associated with the organic material that goes into a digester. However, AD can actually reduce nuisance odours as waste is delivered in closed vessels and vehicles, received in a closed reception area, and the digestion process takes place in a sealed tank. The digestion of slurry, for example, is significantly less odorous than the common practice of storing slurry in pits.

Is AD right for me? 

This website is a good place to start.  There is an AD cost calculator to look at the economics and there are lots of links to useful information and organisations. The key questions for a potential developer are:

  • Do you have access to sufficient feedstock?
  • Is there a market for the digestate?
  • What do you have in terms of good access, storing and handling facilities?
  • Are you willing to take on high capital project with capital rich initial period (i.e. can delayed returns be absorbed in your cash flow model)

 What are the benefits of AD? 

  • It turns waste into a resource. Instead of sending waste to landfill, we can use it to produce energy and fertiliser.
  • It produces fuel. Bio-gas can be used instead of fossil fuels.
  • Fertiliser is produced. Fertilisers are made from fossil fuels. The digestate from this can replace some synthetic fertilisers.
  • It reduces our carbon footprint.The methane produced during AD is burned as fuel, and therefore releases CO2 into the atmosphere.  Because it comes from biomass, this does not contribute to climate change. However, if the same waste was left to degrade in a landfill site, the methane produced could escape into the atmosphere: methane has a global warming potential 23 times larger than that of CO2. Therefore, harvesting and using methane from biomass can help to prevent climate change.
  • It can benefit many different people.  AD potentially benefits the local community, the environment, industry, farmers and energy entrepreneurs and government.

 What are the drawbacks of AD?

  • AD plants are 24-hour operations and as such they need to be fed regularly. Pumps and other machinery also need to be maintained to ensure production is not interrupted.
  • There can be noisedust, and if there are leaks the potential of smells and environmental contamination. However, these issues are strictly controlled by environmental regulations, so should not occur. The liquid part of the digestate contains nitrates and other chemicals which should not be released to water but which can safely be spread to land or processed for wider use.
  • The use of bio-gas also releases CO2, which is a greenhouse gas. However, this is offset because the bio-gas produced in AD replaces fossil fuels when it is used for heat, power or transport. If the waste were land-filled it would naturally rot and release methane, a potent greenhouse gas.


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