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MPhil in Engineering for Sustainable Development

global challenges, engineering solutions

Studying at Cambridge

Markus Graebig

Comparative analysis of land use intensity and environmental impacts of biomass and photovoltaics

This study evaluates which technology – photovoltaics (PV) versus the maize-biogaselectricity route – can mitigate more environmental pressure, assuming that a given agricultural area is dedicated to energy production. Biomass and PV are compared on the basis of a life cycle assessment (LCA), analysing their potential to mitigate environmental burden in relation to conventional technology for power and / or heat generation.

The environmental performance of each system depends on the scenario that is assumed for end energy use. Related to cumulated electric energy output, PV turns out to be superior to biogas in almost all LCA categories (PV, compared to biogas, can mitigate a 15fold quantity of non-renewable energy input and 18 times the amount of green house gases, GHG); only the eutrophication level (about 60% higher) seems to be a downside of PV in comparison to biogas. Even when maize is used for electricity production in connection with very efficient heat usage, and reduced PV performance is assumed to account for intermittence, PV can still mitigate about 4 times the amount of GHG emissions and non-renewable energy input compared to biogas. Soil erosion, which can be entirely avoided with PV, exceeds soil renewal rates roughly 20fold on maize fields. Regarding the overall Eco-indicator 99 (H) score, PV has a more than 100% higher potential to mitigate environmental burden.

At present, the key advantages of biogas are its price and its availability (no intermittence). However, intrinsic problems are likely to prevent biogas from succeeding as the preferred sustainable energy system: Energy crops will keep on competing with food and material production for the best sites, not only inflating food prices, but also intensifying eutrophication and acidification, soil erosion, and the demand for GMO crops. Basically, food and renewable materials should be the preferred applications of biomass. However, biogas has its place within a sustainable energy mix as long as it is produced from bio-waste or manure.