Fuel is Cheaper than Compost
Using biomass as a raw material for SunFuel helps many communities save money
Volkswagen is researching the production of synthetic fuels from biomass — so-called SunFuels — together with the German Federal States of Brandenburg, Hesse and Lower Saxony. The project with the somewhat lengthy title — “Decentralised Biomass Provision from Bio and Green Waste in Lower Saxony for SunFuel Production” — belongs to the important area of raw material acquisition. In the research work for this project carried out by Prof. Heiko Doedens, qualities of bio and green waste are being investigated to see if they are suitable raw materials for producing synthetic biofuel. The existing logistics and preparation technology should be incorporated. In the cost calculation for the prepared biomass, Prof. Doedens expects the processing costs to be the same as before. Investigation results from the project are now available in the form of a study.
In addition to different so-called energy plants, bio and green waste is also being considered for fuel production. This waste is already being gathered extensively in Lower Saxony and turned into high-quality compost. Its continued use in agriculture is uncertain because the limit values for hazardous substances are becoming increasingly stricter for reasons of soil conservation. Consequently a ban or at least limited use of the compost can be expected. Therefore alternatives for the disposal of the green and bio waste are urgently needed to ensure the future of the composting facilities. If the bio waste will be used in SunFuel production, a working collection and treatment system that is already financed by the disposal charges will be available.
Biomass needs to be pretreated for SunFuel
At present, the composting facilities in Lower Saxony can process around 1.45 million tons of biomass each year. Half of this is green waste, for example, green trimmings with a large proportion of wood. The other half comprises almost exclusively bio waste, for example, kitchen waste from private households. Before the green and bio waste can be sent to the SunFuel plant, so-called foreign matter needs to be removed first. The material is broken up or sieved and then dried in preparation. The investigation showed that the bio waste is not as suitable for SunFuel as the green waste because the water content is too high in particular. If the appropriate pretreatment is carried out beforehand, the previously known requirements for SunFuel raw materials can be met. In total, around 382,500 tons of raw biomass is available according to the composting facility operators. Following the necessary preparation to SunFuel raw material, an estimated 210,000 tons of finished product is currently left over for SunFuel production with a 20-percent residual moisture.
The cost of decentral preparation of green waste is currently 35 to 55 euros per ton. In comparison: It costs up to 150 euro per ton to turn the green waste into compost. These costs are covered fully by fees at present. This means for the communities that the lower preparation costs allow the waste disposal fees to be reduced. According to Prof. Doeden’s calculations, the costs of transport to the SunFuel production plant are 10 to 15 euros per ton with an average distance of between 116 and 185 kilometres. By providing a 30-percent subsidy for the composting facility operators, an incentive could be created to actually turn bio and green waste into SunFuel raw material. As a result, the real preparation costs therefore amount to around 21 to 31 euros per tonne. That would still be considerably cheaper than conventional green waste disposal.
Considerable competition from recycling as a fuel
According to Prof. Doedens, a high capacity utilisation of the Lower Saxony composting plants can also be expected in the future. Therefore the plant operators are definitely prepared to also provide raw material for other purposes. In addition, an oversupply of compost is making it difficult to market. Wood-like residual materials such as green waste and sieve residue are actually particularly well suited for SunFuel production, but energy uses (combustion) are providing great competition due to their promotion in the renewable energy act. Bio rubbish is a relatively cheap raw material for biofuel production, but only if the disposal system remains financed through fees as before. Economic incentives would therefore be useful to get a new sales market moving. The theoretical knowledge gained so far should therefore be followed up with a practical test as soon as possible. The operators of the composting facilities are very interested in such a test run.