Biogas from Food Waste
It is our understanding that Food Waste is no longer permitted at landfills starting 2015 in California. Organic Food Waste contains much energy and together with our represented BioTec Waste presorting technology and patented anaerobic fixed bed register UDR technology, we have the ideal processes for converting Food Waste to renewable energy. The produced digestate makes for no odor organic fertilizer that is absorbed by plants more easily. Any remaining waste including cellulose based wood can then be gasified using the WLE process for additional energy gains.
Food Waste is generated at hotels, school and business cafeterias, grocery stores and in every household.
The issue at hand is how to educate the population that generates the waste to understand its value and handle/separate it responsibly from trash. While the separation process in corporations can be dictated and monitored, discipline among the population at large is voluntary…. so, public education in schools, at PTA meetings etc. is required. It is so easy to dispose of the organics with an in sink disposer that grinds it up and flushes it with scarce water down to the treatment plant. Instead it takes effort to fill a digestable plastic bag and set it curbside.
As a result what’s available as Food Waste has plastics, cardboard, metal objects and glass mixed that are not organic and need to be sorted out.
Pre Preparation of Food Waste (10,000 tons per year and above)
BIOGAS Equity 2 offers a technology that was developed with assistance from the German Ministry for Environment. Some 20 plants using this automated presorting technology are in operation in Europe and abroad. Visits can be arranged.
Waste is delivered by truck into the preparation building. This building is equipped with exhaust fans, negative pressure and bio-filters that assure that no smells escape. By pay loader, the waste is fed to a bag opening crusher and subsequently to a special disc-screening station which separates the material at about 80 mm particle size. The material > 80 mm contains practically no organic material while the small fraction contains the majority of the organics but still about 20% of inerts. The fine fraction is transported via magnetic metal separator into the dissolving tank (suspensor). Water is added and by applying high shearing forces, the organic material is disintegrated down to fiber size, thus forming a pasty slurry, while plastics and other inert material remains practically unaffected.¬†This allows the separation from the suspension by screening and sedimentation. The remaining slurry, now practically pure organic material is heated to 70 degree C for hydronization and then pumped into the Upflow digester tank for initial anaerobic fermentation. Under specific conditions of pressure and temperature and with the assistance of methanogenic bacteria biogas is extracted with the remaining forming a valuable, clean and uncontaminated organic compost material. – see Technology tab for more info. The liquid fraction of the slurry is dewatered thus forming the compost substrate while the separated water gets recirculated and reused for dissolving of incoming fresh Food Waste.
Pre Preparation of Food Waste (less than 10,000 tons per year)
BIOGAS Equity offers solutions for pre processing the Food Waste prior to digesting the slurry in its UDR system. Incoming material is dumped into an outside holding pit with an hydraulic cover to contain odor. Heavy material such as glass and metal objects sink to the bottom from where it is occasionally removed. Light material such as plastics and cardboard float to the top for manual removal. The Food Waste is then mixed with recirculated liquid from dewatering the digestate and pumped into a Bio Chop system that grinds up all Waste to less then 12mm.¬† The slurry is then heated to 70 degree C for hydronization prior to being pumped into the Upflow tank of our anaerobic biogas generating process. – see Technology tab for more info.
BIOGAS Equity 2’s UDR anaerobic digestion process is ideal for converting Food Waste into renewable energy. The patented process provides for 2,000m2 of surface area for bacteria colonies to grow and adhere in both the Upflow and Downflow tanks. The recirculation method through the Reflow tank assures complete digestion and extraction of biogas. – see Technology tab for more info. The gained biogas is burned in a CHP engine that provides electricity and heat. For large plants, we offer the option to upgrade the biogas to biomethane to be used as clean burning vehicle fuel or upgraded for pipe line distribution to remote filling stations. If heat cannot be sold, options are available to convert it to additional electricity.
One additional benefit that the UDR process offers besides more biogas extraction in a shorter time frame is the small footprint our plants require. A 450kW plant converting 15,000 tons of Food Waste a year and converting the biogas to electricity, heat and fertilizer requires less than 10,000 sqft of real estate.
A single UDR tank (MonoTube) can process 3,000 tons per year and generate 75kW. This facility fits on 1,000 sqft which makes it practical for an organization that caters to several thousand employees a day such as a university, Apple Computer, Google, Facebook and similar Fortune 500 companies to convert kitchen food scraps to renewable energy, heat and valuable fertilizer by saving on tipping fees.