PDF Publication Title:
Text from PDF Page: 055
Anaerobic Digestion of farm and food processing residues GoodPractice Guidelines Page53 Appendix 8 Walford College: case study Location Walford College Farm, Baschurch, Shrewsbury, Shropshire is owned and operated by Walford College, a county-based further education establishment for agricultural and land-based industries. Concept The 260-hectare mixed farm attached to Walford College includes a 130 dairy cow herd, 160 sows and progeny, plus beef cattle and dairy young stock. These produce some 3000 tonnes of organic manure per annum. Environmentally acceptable disposal of this waste presented a problem. In 1990, the college decided to introduce an integrated farm slurry management system based on anaerobic digestion (AD) to assess its advantages over the previous method of spreading raw manure directly to land. AD involves the breakdown of organic waste by bacteria in the absence of oxygen; products include a methane-rich gas which can be used as a fuel. As part of a three year demonstration project, an AD system incorporating an Enviropower combined heat and power (CHP) facility was installed in 1994, rated at 35 kWe (kilowatts of electricity) and 58kWt (kilowatts of heat) output. Actual output has averaged 18.22kWe for 19.5 hours per day. Approximately 30kWt is harnessed to maintain the digester at the requisite temperature of 35-370C. The system also produces 15m3 per day of treated liquid slurry or ‘liquor’ and 3 tonnes per day of separated fibre. The liquor, which is odourless and easier to handle than raw manure, has an average analysis of 2.32kg nitrogen, 1.32kg phosphate and 5.3kg potash per 1000 litres and is spread on grazing land. The fibre is made into compost for the college’s own use and for sale to garden centres and other customers. T echnology Slurry is fed from the pig and dairy units via flow channels to a reception pit. A chopper pump then pumps the slurry into a 335m3 above-ground digester. Digestion takes 16-20 days. Digestion produces 450m3 per day of biogas which fuels the CHP unit driving an electricity generator; heat is recovered from the engine’s coolants and exhaust system. A stand-by boiler is used to heat the digester in the event of failure of the CHP unit. After digestion, the treated slurry is passed over a sieve separator; the fibre is removed to a composting shed and liquor is fed to a 950,000 litre storage tank. It is planned to use the farm’s existing irrigation main to irrigate the liquor onto the grass fields. Legal and planning requirements The planning application was submitted in December 1993. Specific proposals for the erection of buildings or other works relating to AD are normally determined by the county council in shire areas. At Walford College chicken litter is imported as a supplementary feedstock for the digester when the farm’s dairy herd is in the fields. The application was dealt with by Shropshire County Council. Planning permission was granted in February 1994. Construction Construction work began in February 1994. A single contractor was engaged to supply, install and commission the digester, CHP unit and composting shed. The contractor went into receivership before completion and Walford College engaged other companies to provide the CHP unit and composting shed. The system was commissioned in October 1994. Seed material was imported from a working digester to start the AD process. Operating experience The system requires no more than one hour per day from the cowman, who is very enthusiastic about the installation. Actual repair costs are likely to stabilise as the system settles down and teething problems are overcome. The lack of slurry smells around the unit is noticeable. The area around the digester is cleaner than might be expected from a slurry disposal system. Costs and financing The project is jointly funded by Walford College and the European Community’s LIFE programme. Capital cost Digester CHP unit Composting unit (including site infrastructure and connections) Benefits Value of electricity generated annum 18.22kW x 19.5hrs x 365 days x £.08 Avoided contractors’ spreading costs Value of fertiliser saving to grassland (summer 6 months), nitrogen only 34.8kg/day x 180 days x £.32kg Compost sales Waste hot water 20kW x 20hrs x 365 days x £0.18/kWh Annual income generated Running costs: repairs and callouts Net annual income Labour: 1hr/day @ £8/hr £ 89,349 34,700 9,600 _______ £ 133,649 actual (£) in first 6 months 10,374 2,500 2,004 400 2,628 £15,278 (2,100) £13,178 £(2,920) potential (£) (30kW)17,082 2,500 2,004 (1460m3 x £10/ m3)14,600 £38,814 (2,100) £36,714 £(2,920) The need to allow for addition of labour charge will depend on individual farm case, whether worked in overtime or absorbed in working day etc. For further information contact Ken Dann, Walford College, Baschurch, Shrewsbury, Shropshire SY4 2HL, tel: 01939 260461, fax: 01939 261112.PDF Image | Anaerobic Digestion Of farm and food Processing residues The development of a sustainable industry
PDF Search Title:
Anaerobic Digestion Of farm and food Processing residues The development of a sustainable industryOriginal File Name Searched:
biogas10.pdfDIY PDF Search: Google It | Yahoo | Bing
Capstone Turbine and Microturbine: Capstone microturbines used and new surplus for sale listing More Info
Consulting and Strategy Services: Need help with Capstone Turbine, sizing systems, applications, or renewable energy strategy, we are here to assist More Info
Container Lumber Dry Kiln: Since 1991 developing and innovating dry kilns using standard shipping containers More Info
Supercritical CO2 Lumber Dry Kiln: Compact fast drying in 3 days or less for small amounts of wood and lumber drying More Info
BitCoin Mining: Bitcoin Mining and Cryptocurrency... More Info
Publications: Capstone Turbine publications for microturbine and distributed energy More Info
FileMaker Software for Renewable Energy Developing database software for the renewable energy industry More Info
CO2 Gas to Liquids On-Demand Production Cart Developing a supercritical CO2 to alcohol on-demand production system (via Nafion reverse fuel cell) More Info
Stranded Gas for low cost power Bitcoin Mining Using stranded gas for generators may provide breakthrough low power costs for cryptocurrency miners. More Info
CONTACT TEL: 608-238-6001 Email: greg@globalmicroturbine.com (Standard Web Page)