Can crop residues provide fuel for future transport?

02 July 2021
Advanced biofuel
Water-energy-food nexus
Bioenergy
Bio-based economy

A new publication from MAGIC researchers of the University of Twente examines to what extent crop residues can provide fuel for future transport. Bioethanol production from non-crop based lignocellulosic material has reached the commercial scale and has been increasingly advocated as a possible solution to decarbonize the transport sector. The authors estimate global bioethanol production potential from 123 crop residues in 192 countries and 20 territories under different environmental constraints (optimistic and realistic sustainable potentials) versus no constraints (theoretical potential) on residue availability. They then evaluate how much presently-used transport-related fossil fuels can be replaced with lignocellulosic bioethanol from crop residues, calculate the greenhouse gas emission savings, and determine lignocellulosic bioethanol's land, water, and carbon footprints. 

The findings suggest that the global net lignocellulosic bioethanol output ranges from 7.1 to 34.0 EJ per annum, thus potentially replacing between 7% and 31% of oil products for transport and yielding relative emission savings of 338 Mt (70%) to 1836 Mt (79%). Emission savings range from 4% to 23% of total transport emissions in the realistic sustainable versus theoretical potential. Land, water and carbon footprints of net bioethanol vary between potentials, countries/territories, and feedstocks, but overall exceed footprints of conventional bioethanol. Averaged footprints range between 0.14 and 0.24 m2 land per megajoule (MJ−1), 74–120 L water MJ−1, and 28–44 g CO2 equivalent MJ−1, with smaller footprints in the theoretical potential caused by the exclusion of secondary residues and low price of alternative biomass chains in the sustainable potential.

The authors conclude that the gap between current bioethanol production capacity and the required capacity to match the level of production calculated in this study is large and may require decades to fill while the future supply of residue and the environmental footprint of future lignocellulosic bioethanol production remain uncertain. Even if the theoretical production capacity could be reached, if we rely on current modes of transport with internal combustion engines and feed them as much as possible with crop residue based lignocellulosic bioethanol, we would remain heavily dependent on fossil fuels. Therefore reducing the motorization rate and shifts in modes of transport are necessary to decarbonize the transport sector.

Read the full article here (open access): https://doi.org/10.1016/j.rser.2021.111417.