We received news from REUTER on a publication from Lancaster University researchers about biofuels modeling sustainability and environmental impacts to the air. We revised it and made some comments on the credibility of the conclusions.
The report is still being reviewed in the journal Nature Climate Change, and will be available soon. The main conclusion? Isoprene pollutants to the air can be harmful on Short Rotation Coppice when replacing food crops like maize or wheat.
The study was based on previous work published by the same group as can be read here: Impacts of near-future cultivation of biofuel feedstock on atmospheric composition and local air quality.
Some preliminary analysis from our group:
1) Life cycle comparisons are poor. The main aspect to revise is whether the authors have considered the complete Life Cycle, since most assumptions have not taken into consideration the impact of the traditional crops replaced, the NOx emissions replaced when using biomass from plantations to save emissions from coal or gasoline, neither the impacts to the air from those fossil fuels. The authors have no discrimination between productive and marginal lands, or different logistic chains, technologies, efficiency of the process from biomass to energy, and provide no data on charges allocation in the agricultural phases.
2) A generalization in the conclusions is a second mistake. The information gathered by the authors and the methodological framework used is the same for all Bioenergy chains making little differentiation between crops, technologies and logistics or specific sites and productivity.. Liquid and solid biofuel, annual and perennial crops, biomass to be burned, gassified, digested to biogas, or fermented to produce bioethanol are all part of the same assumptions and most information and details were omitted when concluding on Bioenergy sustainability.
3) The authors suggested that dedicated energy plantations are assumed to replace traditional crops in EU which is something not totally clear in our perspective. For example, in Spain there are about 4M hectares of available lands for energy plantations, in Poland and other countries, fallow and abandoned lands are also available and we found difficult to sustain such assumption.
4) The report mentioned that same fertilizer rates were considered for all cases (cereals, short rotation Coppice, maize, etc) not discriminating sites, soils, climate conditions and even productivity (that requires different fertilization regimes) or irrigation. Life cycle assessments in bioenergy chains worldwide have been providing evidences on large variability on environmental impacts depending on their specific performance in each case.
5) Many assumptions are uncertain. The authors concluded that isoprene derived emissions from biofuel production will be a major pollutant with impact to the air that need to be considered in the life cycle assessment and next policy making. They wrote: “Growing biofuels is thought to be a good thing because it reduces the amount of carbon dioxide in the atmosphere” and added: “What we’re saying is ‘yes, that’s great, but biofuels could also have a detrimental effect on air quality”. This is something reasonable, but the report never demonstrated why or how those impacts will be produced. They only made assumptions and run some models simulating deaths and economic losses. The preliminary conclusions in the abstract disseminated in REUTER news, talked about “replacement from grasses and annual crops” with broadleaf species like eucalyptus, poplar and willow. Nevertheless the conclusions talk about biofuels and energy crops which can be Miscanthus, Switchgrass or many other not-broad leaf species. They never assumed NOx to be higher in an annual food crop like wheat or maize compared to short rotation forestry in EU or other perennials, which is an extensively studied topic in literature.
6) A strict comparison of scenarios and reported statistical data used in the models is not present in the study. The authors have never considered what are the savings from bioenergy regarding replacement of fossil fuels (less coal, less emissions, less NOx, less isoprene, less deaths and also an impact on economy). Furthermore, they assumed no changes in NOx from annual crops to SRC based on an assumption which is same fertilizer rates. No consideration of the perennial aspect was taken into account when comparing Short rotation coppice to wheat or maize emissions (even if the first crops require soil preparation (ploughs) every single year and short rotation poplar or willow lifetime is about 15 or 20 years). Again the conclusions are dubious and based in assumptions we disagree. The authors never reported R Square (R2) of their models, and they use several models that link atmospheric data with crops and emissions. In most of them the data and assumed effects are input to other models, and many of those models have been criticized, including those of IPCC and IIASA.