Although AD plants are in use on thousands of farms elsewhere in Europe, none of these plants have been designed to deal with the problems associated with processing animal waste and many are therefore beginning to fail.However, with fre-energy\’s designed AD plant at Lodge Farm, there is no requirement for the system to be regularly shut down whilst the digester tank has to be emptied. Consequently, Lodge Farm has been able to avoid having to allocate valuable land, which is best served to sustaining the farm’s core dairy business, on which to grow crops as feedstock for the plant.
Located on the outskirts of Wrexham, North Wales, Lodge Farm comprises 1100 acres given over, on a fully organic basis, to a herd of 650 dairy cattle and has been running its AD plant for over four years. The fre-energy digester generates a reliable and constant production of energy 24 hours a day, 365 days a year, with a generation capacity of 160kw of electricity and 200kw of heat. In addition to the energy used for the AD process, around one fifth of the electricity and 50kw of heat are used on site to power the farm, on-site engineering business and fre-energy office.
Surplus electricity is exported to the National Grid (sufficient to supply around 80 houses) and is eligible for the Feed in Tariff (FiTs). As some of the energy is utilised as heat it is also eligible to receive income under the Renewable Heat Incentive (RHI) that pays a fixed fee for every kilowatt of heat produced. The payment is effectively to reward using alternative renewable energy sources to fossil fuels.
Continuity of energy supply and, therefore, RHI and FiT income generation, is also assured by the ability of the plant to process high strength feed-stocks, such as chicken litter and food waste. These feed-stocks have the potential to create foam which, if it enters the gas output pipes, can irreversibly damage the VCHP engine and compromise the AD process. The system at Lodge Farm allows the foam to be removed from the gas space without the need to reduce the digestate level in the tank.
On-farm AD
According to Richard Tomlinson, MD of fre-energy, \”We have developed unique technology, for which worldwide patents have been granted, to enable farms to process their animal slurry, which would otherwise have to be disposed of. Although AD plants are in use on thousands of farms elsewhere in Europe, none of these plants have been designed to deal with the problems associated with processing animal waste and many are therefore beginning to fail. As farmers ourselves, we have invented technology that is proven to work on farms and have to date installed plants at 3 further farms in the UK.”
On-farm AD has enormous potential to deliver renewable energy from bio-gas and to lessen the carbon footprint of farming, whilst at the same time reducing greenhouse gas pollution from organic wastes and returning valuable nutrients back to the land. Fre-energy is in a unique position to play a major role in transforming the UK agricultural and environmental industries.
Where on-farm digestion is successful in Europe, it has been as a result of subsidies for the energy produced and guaranteed long-term markets for it, allowing investment to be made on the basis of a commercially sound business plan.
This has contributed to a huge growth in farm digesters with, for example, more than 4000 plants currently operating in Germany. Such success, however, has been based on the production or import onto the farm of high-energy crops such as maize for co-digestion, rather than on the processing of slurry alone.
Food or fuel?
This, of course, then begs the question of whether we should be using our precious land for food or for fuel. In a world where the population is projected to grow by around 2bn to over 8bn within the next generation, the global demand for food will inevitably continue to rise and the use of increasingly scant agricultural land for the production of electricity or bio-fuel will most likely be socially and politically unacceptable.
In the words of the Government Review of Waste Policy in England 2011, “our aim is to get the most energy out of genuinely residual waste, not to get the most waste into energy recovery.”
With operation and maintenance costs of just 4.7p/kW the fre-energy AD system therefore generates a significantly higher margin than other digesters.
This story was published by the CIWM Magazine: http://www.ciwm-journal.co.uk/archives/6316
