Micro-Biogas is the technology currently under development by Future Power These much smaller digesters are more suitable for small agricultural businesses, food distributors and the food industry and eventually groups of condominiums. A large range of some 80 diverse sources of biomass can be fed to the digesters simultaneously, providing great operational flexibility. See the detailed pdf proposal in Italian by Future Power Ltd  addressed to processing waste created by islands and small isolated villages Mini-Digester for Solid Fermentation in Biogas. A second proposal using this technology is addressed at organic waste created by supermarkets and similar business. They both use the Swiss Renegon technology.


Recycling of organic waste – Part II

See below for Part I pdf

Q.4 What needs to go into biogas digesters? Have you got any of these precious resources?

Fruit and vegetable waste from canning and processing industries – including potatoes, sugar beet, oilseed rape; coffee and cocoa beans etc; Mash from breweries and wineries; Post harvest residues (stalks, straw, leaves etc); Waste from flour, bread and pastry  makers; Waste from milk, cheese and yogurt industry; Spent vegetable oils; Waste from processing olives for oil extraction; Grass mowings and cuttings from public and privately maintained parks and gardens; Unsold plants and flowers from wholesale and retail operations; Unsold fresh fruit, vegetables and meats from wholesale markets and supermarkets; Food waste from from restaurants, kitchens, bars etc; Meat waste and gelatine from slaughterhouses and meat processing plants, including manufacture of vegetable and meat stocks and glues; Slurry and manure from cattle, pigs, horses, sheep and chicken rearing; Organic fraction of urban waste from differential collection of domestic waste; Organic sludge from sewerage purification plants and industrial plants; Glycerol from the production of diesel…..and much more.  If yes, then you’re rich!

The European Commission is encouraging Member States to implement existing waste legislation more effectively. Waste management and recycling industries in the EU had a turnover of € 145 billion as long ago as 2008, representing around 2 million jobs.  See the article in Italian in publication BioEcoGeo oct/nov 2015 by Claudia Berrini interview of Ing. Marco Baudino, MD of Future Power Ltd.

Kroger is the largest supermarket chain in the U.S Kroger supermarket chain Food waste will help power its 6 ha Ralphs/Food-4-Less distribution center. An anaerobic digester will process more than 55,000 tons of waste a year, providing 20% of the facility’s energy. The system also will reduce lorry trips by more than 500,000 miles each year – the same lorries that deliver food to supermarkets from the distribution center will make their return trip with food waste from supermarkets. This biogas system is designed and operated by FEED Resource Recovery, Inc. Feed Resource Pay-back is said to be 5 years translating to an 18.5% return. Summary from an article in Sustainable Business News, May 21, 2013. Sustainable Business News

Q.5  Most food products are wrapped, contained and presented in plastic and other materials that are not biodegradable. What must be done?

Today, these industries, wholesale and retail operations have to separate non biodegradable containers and packaging from the organic resource. The cost of separation has to be substracted from the value of the energy generated from the organic fraction. As a result, new biodegradable materials will be realized and the cost of separation greatly reduced since in many cases, foodstuff, containers and packaging can all be thrown together into the digester at the same time. The other requirement is the need to gather, compact and store the organic waste resources in a place on-site until they can be collected or delivered to the nearby biogas plant. This will be considered later.

 Q.6 What Biogas technologies are the best?

Depends on each given circumstance. However, the anaerobic digestion technology developed by the Swiss Company Axpo-Genesys AG is advantageous due the small, flexible (modular) yet intensive functioning of its biogas installations. The digesters are relatively small and can be added to as the sources of organic waste increase either on the one location where the plant is constructed or from various external sources.  This fact eases some of the potential problems associated with larger operational designs where balancing the supply and demand for a constant feed of large quantities of biomass (organic waste) becomes much more critical. Other important technologies are on the market or under development.

Q.7 What can we put into the ‘Risotto’ that goes into the digesters?

A wide range of different organic waste resource can be used in the same digester. A certain percentage of the material fed to he digestor must be in a liquid form, for example, animal/sewage slurry or alternatively, dry organic waste can be first liquified.  At all events, the dry component of this  ‘risotto’ should not exceed 12-13% of the total. Waste plant material, for example: grass cuttings, soft prunings, unsold flowers and plants, vegetables and fruit are ideal because they contain only very low levels of lignin. Other plant waste that include woody materials, for example: old leaves, small branches etc, is first treated to separate out the woody fraction.

A 100 Kw plant from one Company with a digester of 1200m2 has a payback period of 5-6 years. This takes into account the production of about 732,000 Kwh/year of electricity and 488,000 Kwh/year of disposable heat energy, the latter being sufficient to heat 20 appartments for a year. A larger 190 Kw plant, will generate 30% more energy and provide a shorter payback period of 3-4 years. To these details, government economic incentives need to be considered. This provides an economic and flexible solution to the generation of alternative energy, one that operates 24 hours round the clock and is not dependent on the presence of  sun, wind or water.

Q.8 What comes out at the other end of the digesters?

1  Electricity A little of the electricity generated is used to operate the plant itself, some can be used to meet the needs of the farm and living quarters on the site of construction, given that the income per unit of energy obtained from selling it to the national or local grid is greater than the cost of the ordinary supply. The majority of the electricity generated is supplied to the national or local grid at a previously agreed fixed price.

2 Heat Waste heat from the cogeneration motor (as much as 30% of the energy generated by internal combustion engines is lost as heat) is transferred via a heat exchanger to piped hot water. Some of this can be used to maintain the necessary temperatures in the biogas digester; 35°C in the case of mesophyll bacteria, 55°C for thermophyll bacteria. The rest is available as piped hot water to heat  farm buildings, greenhouses, and living quarters.  The piped hot water can be considered a feasible source of heating for greenhouses within a radius of about 1 km from the biogas installation.

3 Compost The liquid sludge that exits from the biogas digester after the anaerobic digestion, is collected.  It is then passed through a centifugal separator that fractionates the sludge into solids that can be bagged and used as a general compost. The liquid fraction can be used as a field dressing or in fertirrigation. In both cases the principale nutritive elements NPK are not affected and the product is totally safe to use in organic production of vegetable and fruit. An added bonus is the total lack of unpleasant ammonia smells.

4  Disposal Biogas installations provide a service to the environment and to society by removing organic waste and turning it into energy. The traditional disposal of organic waste in landfill sites adds to the carbon footprint by burning of fossil fuels in its transport, often hundreds of miles from its origin. This costs money! Waste in landfill sites causes pollution if  it drains into underlying acquifers or by releasing methane gas to the atmosphere. The leaching of these organic substances into neighbouring fields is damaging to plant diversity.

BIOGAS Part I pdf

06 Weltec Biogas plant for vegetable grower

01 Agricultural waste and biogas pdf

02 Biogas from domestic and urban waste pdf

03 Biogas using waste from wholesale markets pdf

04 Biogas from waste for greenhouses in Canada pdf

05 Biogas Urban Farm Chicago pdf

Edward Bent ©2012 | HORTCOM


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