Building an anaerobic digestion plant is a large and complex project that requires teams of specialists to handle the many aspects of the project—from conception and planning to implementation.
Speak with one of our high voltage electrical engineering Anaerobic Digestion Specialists today.
The word ‘anaerobic’ (or anoxic) means oxygen deficient (or oxygen depleted). Recycling organic wastes through anaerobic digestion is a nature-based solution that is part of the natural carbon lifecycle.
The civil and electrical works are referred to as the Balance of Plant (BOP). The electrical works are designed and installed with a high voltage specialist contractor like Powersystems in partnership with the civils team.
Experience in the design and installation of high voltage electrical infrastructure has placed Powersystems in a position ideally suited to install anaerobic digestion balance of plant contracts.
To date Powersystems have connected over 97 anaerobic digestion sites throughout the UK with many more coming online in the near future.
Powersystems have connected Anaerobic digestion generation plants to the grid, powered from commercial food waste, energy crops, dairy, pig & poultry waste in the farm based sectors.
We have worked alongside the major technology providers in delivering both grid connections and onsite customer electrical works.
Typically, these schemes will be cable connected to the local distribution companies high voltage network and electrically metered onsite, from there a bespoke site distribution system is designed and installed to meet the AD Plants requirements. This system would usually be comprised of a generation transformer and main Low Voltage (LV) distribution board, providing electrical circuits to the site load center and AD plant.
Anaerobic digestion infrastructure consists of the below points to be considered in your AD project.
Civil works
Electrical works
A future featuring increasing levels of renewable energy will depend on a range of technology types that can use the UK’s natural weather, geography, and resources. Alongside power sources like wind and solar, a stable and environmentally friendly energy system also needs renewable alternatives without the intermittency of weather-dependent sources.
Anaerobic digestion (AD) is the ready-to-use-technology that, by recycling organic wastes, cuts emissions in the hardest to decarbonise sectors of our economy, including heat, transport, agriculture, and waste management. The technology has a huge potential to mitigate the climate crisis we face by:
The AD sector has committed to reduce its GHG emissions:
AD systems are highly flexible, scalable and extract the greatest value out of organic wastes. AD can operate at sizes from that of a test tube to tanks of many thousands of cubic metres. As such it is adaptable and can just as well address 9 of the 17 Sustainable Development Goals in the remotest parts of the global south to the organic wastes created by world cities such as New York.
~ Powersystems high voltage specialist electrical engineering team have connected 97 anaerobic digestion plants in the UK ~
There are many types of AD systems, depending on the feedstock. They can be designed to treat wet or dry wastes – known as wet-AD and dry-AD – or a mix of both. In countries where dry-AD is the norm the AD process often includes a composting phase.
Anaerobic digestion 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 biogas, 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.
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).
Mesophilic or Thermophilic
This refers to the temperature at which the digester operates. A thermophilic digester operates at 50 to 60°C. Gas production is quicker at this temperature with shorter retention times and therefore throughput can be increased resulting in a similar gas output being achieved with a smaller digester tank. Thermophilic
digesters more effectively kill pathogens in the feedstock where high risk feed stocks are used. They will however use a higher proportion of the energy produced to maintain the digester temperature
Mesophilic digesters operate at 25 – 45°C. Retention time of the feedstock within the digester is higher for a similar gas yield and therefore a larger vessel is required. Where digestate is stored as it exits the digester for seasonal spreading and the store is enclosed, gas collection from the store can compensate for a reduced residence time.
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, acetogenesis and methanogenesis.
The result is that the biogas 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 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 waste materials.
Anaerobic digestion can be applied to a range of natural biodegradable materials, including food waste, slurry, sewage sludge and manure.
Anaerobic digestion 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.
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.
The average farmer’s options to fully and economically utilise their slurries in an environmentally friendly manner are further compromised by the fact that:
Up until April 2019, the primary incentive available to farmers was the Feed-In Tariff (FIT). Which was based on the installation of an AD plant and 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 biogas from the AD process.
Anaerobic digestion isn’t just some new fad, this technology has 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 May 2022.
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.
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.
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 as well as food waste from retailers and biodegradable household waste.
The process works:
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.
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.
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.
Read the latest anaerobic digestion case studies from Powersystems in anaerobic digestion projects.
Powersystems were appointed as Tamar Energy’s preferred partner in delivering the grid connection to the new Basingstoke Anaerobic Digestion facility, working under FLI Energy who were the EPC for the project.
Three anaerobic digestion (AD) facilities from Tamar Energy with a combined capacity of 6 MW have completed construction and are entering the commissioning phase at locations across the UK.
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