29.04.2010

New tool estimates economic feasibility of biogas production

Quelle: European Commission

Researchers have developed a new tool to evaluate the economic viability of biogas production from agricultural waste, such as manure and straw. It focused on a co-digestion method where farmers treat several types of waste together, including industrial by-products, such as glycerol.

The anaerobic digestion of agricultural waste is a promising method to treat waste whilst also efficiently producing energy with little pollution. It is a biological process during which organic carbon in the waste is converted to CO2 and methane without the presence of air. The product is biogas, which can be used as energy. It is typically a mixture comprised mainly of CO2 and methane with small amounts of other gases.

Biogas production is a complex process involving several stages. To develop the tool the research considered a hypothetical example of biogas production from three feedstocks: fresh pig manure, wheat straw and glycerol, which is a by-product of biodiesel manufacture. It estimated the amount of biogas produced per year from the three different feedstocks and totalled this to calculate the net energy produced, having subtracted the electricity used during production.

The energy exported to the grid was estimated to be 31,676,387 KWh per year. The researchers noted that their estimations used figures for the maximum potential biogas production for each individual feedstock and that during continuous anaerobic digestion of all three feedstocks together the yields may be lower.

In order to evaluate the economic viability the study considered the various costs associated with this example of biogas production. Three types of costs were considered:

• Total plant costs - these included costs of basic equipment, buildings, piping and electrical works.
• Total project cost - this included development costs, such as loans, and other equipment, such as cleaning systems.
• Operational costs and revenues - these included personnel costs, maintenance costs and costs of the feedstocks.

Considering all the costs the total yearly income from this example of biogas production was estimated to be €2,814,128. This included the sales of electricity and sales of compost produced during the process, as well as money received from fees charged to those that bring the waste to the plant or gate fees.

Although three specific feedstocks were used in the analysis, this evaluative tool could consider a variety of feedstocks, including organic waste, such as manure, industrial by-products, such as distillery waste and glycerol, and energy crops, such as maize and sorghum. By taking into account their different characteristics, the tool can estimate the revenues gained from the energy produced and from the compost and liquid fertiliser. As such it can help in the first step of deciding whether to invest in a biogas plant and also when deciding which feedstocks would be most appropriate.

Further information:

sotokar@mail.ntua.gr