Systems analysis for sustainable bioprocess engineering and biotechnology

Clean energy can support the circular economy to achieve Sustainable Development Goals while tackling climate change. Biomass is promoted as an eco-friendly feedstock for biofuel production to facilitate energy transition. However, sustainable production of this renewable energy is only possible if the appropriate biomass and engineering approaches are combined to work well for people and ecosystems worldwide. Thus, system thinking approaches are urgently needed to go beyond the silo mentality, green chemistry, green biotechnology and “safe and sustainable by design”, among others. Systems thinking underpins bioresource systems analysis, and one example is the promising production of bioethanol from arid plants at an industrial scale. This study joined agriculture and a biorefinery to create an agrobiorefinery system whose energy efficiency was assessed by applying energy balances, energy returns on investment and cumulative energy demand. Prickly pear cactus (Opuntia ficus-indica) is farmed in arid regions and used as raw material in biorefineries for ethanol production. The fertilisers considered are inorganic or organic, whereas the biorefineries considered are traditional (with acid pre-treatment) or enhanced (recycled ionic liquids). The new agrobiorefinery is cleaner and showed an energy return on investment three times that of the traditional agrobiorefinery. The yield of ethanol per gramme of prickly pear cactus outcompeted that of rice straw, algae, bagasse and corn stover. This novel agrorefinery concept reduced by a third the energy used by the traditional biorefinery, specifically in the stages of ethanol purification, biomass pretreatment and conversion. Systems thinking can support sustainability efforts based on biotechnology and bioprocessing engineering to improve energy efficiency. Sustainable agrobiorefineries could deliver green energy, sustainable products and services for climate risk mitigation and sustainable development.