Biofuels go urban

The major irony of biofuels is that while their feedstocks are grown in rural areas, they are mainly utilized, whether for transportation or energy production, in urban areas, which are responsible for 70% of global energy use. This irony is at the heart of many of the ongoing controversies surrounding biofuels, including fuel verses food, land use change and energy efficiency.

In which case, perhaps the answer is to do away with this irony and grow biofuel feedstocks in urban areas. This would leave arable land for growing food crops, help prevent wilderness areas from being converted into fields and greatly reduce transportation needs, as the feedstocks would be grown and used in the same place. Those living in urban areas would also benefit, as the biofuel feedstocks could help to protect against flooding, reduce pollution, enhance biodiversity and generally provide a greener and more pleasant living environment, with all the associated reductions in stress and increases in wellbeing.

But is it feasible? This is what a team of UK researchers, led by Jill Edmondson at the University of Sheffield, decided to find out, by modelling how much biofuel feedstock could be grown in 10 cities across the UK: Southampton, Bristol, Swansea, Milton Keynes, Leicester, Nottingham, Sheffield, Liverpool, Newcastle and Edinburgh.

To determine how much space would be available for growing biofuel feedstocks, they analyzed satellite images of the 10 cities, in order to find areas that were currently covered in vegetation and so could easily be converted into growing biofuel feedstocks. Obviously, not all of these areas could actually be used, including those designated as nature reserves, common land, sports fields or private gardens, which Edmondson and her team tried to identify and exclude. This left areas such as parks, roadside verges and waste ground.

In total, they found that around 10% of the urban greenspace in the 10 cities is potentially suitable for growing biofuel feedstocks, of which 3% could be found in the built-up areas of the cities. Swansea had by far the largest area available, almost three times more than Edinburgh, which had the next largest area, while Southampton had the least.

Edmondson and her team then calculated how much of three commonly grown biofuel feedstocks – Miscanthus grass, short rotation coppice willow and short rotation coppice poplar – could be grown on this space, using yield figures that took into account the different climates at the 10 cities. As they report in a paper in Global Change Biology: Bioenergy, the amount of feedstock that could be produced by the cities ranged from almost 50,000 oven dried tonnes (ODTs) per year for poplar in Swansea to just a few thousand ODTs per year for poplar in Southampton.

Extrapolating these findings to the UK as whole revealed that all the country’s urban areas should be able to grow sufficient biofuel feedstocks to meet almost a fifth of the predicted demand for biomass by combined heat and power (CHP) plants in 2030. The researchers think the same should be broadly true for many other countries with extensive urban areas.

So, while this study shows that urban areas can only grow a minor proportion of the required biofuel feedstock, they can still make an important contribution, thereby reducing the amount of arable land required for growing biofuel crops and the amount of wilderness that needs to be converted. Various practical issues would need to be dealt with, however, for this to happen.

Residents may, for instance, object to losing their park space to biofuel crops. But this could be partly mitigated by planting rows of poplar or willow trees, which are more aesthetically pleasing than Miscanthus grass, and ensuring residents still have access to the park. Residents may also object to the increased noise from planting, maintaining and harvesting the crops.

Many of the growing spaces in urban areas would also be quite small, making them less economically viable, but this could be offset by the reduced transportation costs. In any case, as urban areas will increasingly need biofuel crops to help meet their energy requirements, it is surely only fitting that they should help to grow them.

The views represented here are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd. or of the SCI.