Biofuel production is a sustainable source of renewable power, however the use of nitrogen-heavy fertilizers greatly increases its net energy use and carbon dioxide emissions. This study revealed that, by using composted waste from urban, municipal, and industrial sources as fertilizer for biomass feedstock, the environmental and economic sustainability of biofuel production could be greatly improved (Butterworth 2009). Jenny Ward
Butterworth, W. R. 2009. Sustainable biofuel production derived from urban waste using PSCC. Biofuels, Bioproducts, and Biorefining 3, 299–304
The author uses the Bates family farm, a member of the Land Network group, as an example of a farm that relies on photosynthetic carbon capture and storage (PCCS) to reduce its net carbon emissions to almost zero by using urban ‘wastes’ as fertilizer for oilseed rape. This crop is harvested using noninvasive practices and then converted into biodiesel, producing enough biofuel to satisfy all the energy needs of the farm. The article compares the closed energy loops for different methods of turning crops into biofuels: using mineral fertilizers, using wastes, and using PCCS in soils. Finally, nitrogen leakage levels from ‘controlled waste’ fertilizers were measured and compared among several other farm sites within the Land Network.
PCCS is a practical, economically feasible way to sustainably produce both biofuels and cash crops on a farm. Ten percent of the Bates’ farm is dedicated to oilseed growth for biofuels production, and the other ninety percent of the land is used to harvest food crops. About 300 tpa of ‘waste’ from local municipal and industrial sources can make 250 tonnes of compost, which is enough to fertilize 1 ha of oilseed rape. In turn, this 1 ha of land can produce 1 tonne of biofuel, which when burned, emits 5 tonnes of CO2. The PCCS process in the soil however, sequesters 70 tonnes of CO2, resulting in a net storage of 65 tonnes of CO2 in the ground, forming a carbon sink called a ‘humus’. This facilitated process used on the farm mimics the naturally occurring process in the soil between hyphae and plant roots.
The waste sources are in close proximity to the farm, reducing logistics expenses and making this process more economic. Also, the harvest produces all the biofuel the Bates’ need to power all their other processes on the farm, making the system environmentally sustainable. Furthermore, at most farms the amount of nitrogen that leaks into the ground from the compost is negligible, especially when compared to the amounts leaked by mineral fertilizers.
Overall, the use of urban wastes as compost for sustainable biofuel production should explode as a renewable energy source, once restrictive environmental legislations are overcome and techniques to monitor the land onto which wastes are recycle are improved.