Net Energy Analysis and Techno-Economic Assessment of Co-Production of Bioethanol and Biogas from Cellulosic Biomass

An inclusive trend study of techno-economic analysis of biofuel supply chains

Biofuels have gained much attention as a potentially sustainable alternative to fossil fuels to tackle climate change and energy scarcity. Hence, the increasing global interest in contributing to the biofuel supply chain (BSC), from biomass feedstock to biofuel production, has led to a huge amount of scientific production in recent years. In this vein, techno-economic analysis (TEA) of biofuel production to estimate total costs and revenues is highly important for transitioning towards a bioeconomy. This research aims to provide a comprehensive image of the body of knowledge in TEA evolution within the BSC domain. To this end, a systematic science mapping analysis, supported by a bibliometric analysis, is carried out on 1104 articles from 1986 to 2021. As a result, performance indicators of the scientific production within the target literature are presented to explain how this literature has evolved. Besides, thematic trends and conceptual structures of TEA of biofuel production are discovered. The results show that (i) biofuel production and consumption need promotion through tax measures and price subsidies, (ii) the development of cost-competitive algal biofuels has faced many challenges over recent years, and (iii) TEA of algal biofuels to identify commercial improvements and increase the economic feasibility is still lacking, which calls for more in-depth investigations. Consequently, current challenges and future perspectives of TEA in the BSC domain are rendered. The provided insights enable researchers and decision-makers involved in BSCs to (i) capture the most influential contributors to the field and (ii) identify major research hotspots and potential directions for further development.

Modelling and Environmental Profile Associated with the Valorization of Wheat Straw as Carbon Source in the Biotechnological Production of Manganese Peroxidase

Interest in the development of biorefineries and biotechnological processes based on renewable resources has multiplied in recent years. This driving force is the result of the availability of lignocellulosic biomass and the range of applications that arise from its use and valorization. The approach of second-generation sugars from lignocellulosic biomass opens up the possibility of producing biotechnological products such as enzymes as a feasible alternative in the framework of biorefineries. It is in this context that this manuscript is framed, focusing on the modelling of a large-scale fermentative biotechnological process to produce the enzyme manganese peroxidase (MnP) by the fungus Irpex lacteus using wheat straw as a carbon source. The production scheme is based on the sequence of four stages: pretreatment of wheat straw, seed fermenters, enzyme production and downstream processes. For its environmental assessment, the Life Cycle Assessment methodology, which allows the identification and quantification of environmental impacts associated with the process, was utilized. As the main finding, the stages of the process with the highest environmental burdens are those of pretreatment and fermentation, mainly due to energy requirements. With the aim of proposing improvement scenarios, sensitivity analyses were developed around the identified hotspots. An improvement in the efficiency of steam consumption leads to a reduction of environmental damage of up to 30%.

Enhanced Energy Recovery from Food Waste by Co-Production of Bioethanol and Biomethane Process

The primary objective of this research is to study ways to increase the potential of energy production from food waste by co-production of bioethanol and biomethane. In the first step, the food waste was hydrolysed with an enzyme at different concentrations. By increasing the concentration of enzyme, the amount of reducing sugar produced increased, reaching a maximum amount of 0.49 g/g food waste. After 120 h of fermentation with Saccharomyces cerevisiae, nearly all reducing sugars in the hydrolysate were converted to ethanol, yielding 0.43–0.50 g ethanol/g reducing sugar, or 84.3–99.6% of theoretical yield. The solid residue from fermentation was subsequently subjected to anaerobic digestion, allowing the production of biomethane, which reached a maximum yield of 264.53 ± 2.3 mL/g VS. This results in a gross energy output of 9.57 GJ, which is considered a nearly 58% increase in total energy obtained, compared to ethanol production alone. This study shows that food waste is a raw material with high energy production potential that could be further developed into a promising energy source. Not only does this benefit energy production, but it also lowers the cost of food waste disposal, reduces greenhouse gas emissions, and is a sustainable energy production approach.