Sustainable systems from prickly pear cactus nopales

The challenges from climate change require well-coordinated global efforts to impulse a circular economy for achieving Sustainable Development Goals. System approaches like those bringing together agriculture and biorefineries are needed to propose environmentally friendly and energy efficient solutions. Biomasses from the first to fourth generations look insufficient to meet current demands on products, energy, power and heat. Brown biotechnology could offer opportunities to exploit plants from arid regions. For instance, prickly pear cactus nopales. These strong invasive cacti are known for requiring comparatively less water, energy, care, carbon footprint and aggrotech than other biomass feedstocks. It seems possible to propose a novel sustainable biorefinery strategy using sustainable nopales. Well-designed systems can integrate experiments and assessments of realistic scenarios based on life cycle assessment, energy balances and efficiency. This enables a cleaner design for ethanol production from nopales in tune with the circular economy and sustainable development. We studied four realistic scenarios of systems blending agriculture-biorefinery, considering two fertilisers, two pretreatments and two operational modes. The scenarios were evaluated in terms of environmental effects via LCA and efficiency of storing energy in the ethanol molecule. Traditional acid hydrolysis and neutralisation do not lead to cleaner and energy efficient ethanol producing systems. Ionic liquids could offer a positive opportunity if fit-for-purpose chemical engineering designs are deployed. The best scenario considers organic fertilisers, ionic liquids and recycling and reuse of materials. It leads to a cleaner and energy efficient agriculture-biorefinery system for ethanol production. Also, it had the lowest impacts on environmental potentials such as acidification, eutrophication, global warming and more. This design also used the lowest amount of energy per unit of energy stored as ethanol fuel. Besides, it showed the best energy efficiency to capture net energy as ethanol fuel by three-fold compared to the worst scenario. Systems bringing together agriculture and biorefineries with fifth generation biomasses like nopales and novel biomass pretreatment can deliver better solutions to help people, the environment and the climate.