Conversion of vine shoots into bioethanol and chemicals: Prospective LCA of biorefinery concept

Balanced water and heat energy recycling by full evaporation of wastewater (FEW) in dry biorefining processes of lignocellulose biomass

Lignocellulosic biorefinery technology requires minimum energy consumption and wastewater generation to overcome challenges in industrial applications. This study established a rigorous model and a comprehensive physical property database of dry biorefining process on Aspen Plus platform for production including L-lactic acid, citric acid, sodium sugar acids, amino acid, and ethanol based on the experimental data. Full evaporation of wastewater (FEW) approach was proposed to completely replaced the external steam supply, and significantly reduced the freshwater input by 67% ∼ 85% and wastewater generation by 64% ∼ 89%, depending on the specific products. The carbon-neutral heat energy from lignin residue combustion generates an extra heat output of 1.098 ∼ 4.772 GJ per ton of dry wheat straw (DW) after all the heat energy needs of the biorefinery process and FEW treatments are satisfied, equivalent to a reduction of 0.219 ∼ 0.952 kg CO2 eq/kg DM emission. This study provided a self-consistent solution for water and energy balance in biorefinery processes.

Paradigm of engineering recalcitrant non-model microorganism with dominant metabolic pathway as a biorefinery chassis

The development and implementation of microbial chassis cells have profound impacts on circular economy. Non-model bacterium Zymomonas mobilis is an excellent chassis owing to its extraordinary industrial characteristics. Here, the genome-scale metabolic model iZM516 is improved and updated by integrating enzyme constraints to simulate the dynamics of flux distribution and guide pathway design. We show that the innate dominant ethanol pathway of Z. mobilis restricts the titer and rate of these biochemicals. A dominant-metabolism compromised intermediate-chassis (DMCI) strategy is then developed through introducing low toxicity but cofactor imbalanced 2,3-butanediol pathway, and a recombinant D-lactate producer is constructed to produce more than 140.92 g/L and 104.6 g/L D-lactate (yield > 0.97 g/g) from glucose and corncob residue hydrolysate, respectively. Additionally, techno-economic analysis (TEA) and life cycle assessment (LCA) demonstrate the commercialization feasibility and greenhouse gas reduction capability of lignocellulosic D-lactate. This work thus establishes a paradigm for engineering recalcitrant microorganisms as biorefinery chassis.

A life cycle assessment of CCU process to produce a nanocomposite from ethanol plant CO2 emission

The use of rubber septa for controlled release of semiochemicals has raised important discussions about their efficiency and environmental impact since they are composed of fossil raw material. The life cycle assessment (LCA) of the synthesis of a nanocomposite type calcium nanocarbonate/Kraft lignin (NC-CN-KL) obtained from CO2 capture aimed to quantify the environmental loads involved in the production process. The synthesis evaluated by the LCA was performed on a laboratory scale, since it is a synthetic route classified as technological readiness level 4 (TRL-4) and is in the study and development stage. The LCA was performed according to the principles of the ISO 14044/2006 series of standards, from 101.854 g of nanocomposite as a functional unit. The limitations of the study arose from its synthesis scale, absence of LCA data on the rubber septa and other nanocomposites. The results obtained in the LCA identified electricity and other energy generation processes as the largest contributors to environmental loads for all environmental impact categories studied and suggest that research should focus on these inputs when choosing the sources used in energy nanocomposite formulation processes. LCAs for this synthesis to obtain NC-CN-KL should be carried out on a pilot scale, and it is expected that this work will contribute to the formulation of the material and decision-making, especially regarding the choice of the energy matrix.

Review of methodological decisions in life cycle assessment (LCA) of biorefinery systems across feedstock categories

The application of life cycle assessment (LCA) to biorefineries is a necessary step to estimate their environmental sustainability. This review explores contemporary LCA biorefinery studies, across different feedstock categories, to understand approaches in dealing with key methodological decisions which arise, including system boundaries, consequential or attributional approach, allocation, inventory data, land use changes, product end-of-life (EOL), biogenic carbon storage, impact assessment and use of uncertainty analysis. From an initial collection of 81 studies, 59 were included within the final analysis, comprising 22 studies which involved dedicated feedstocks, 34 which involved residue feedstocks (including by-products and wastes), and a further 3 studies which involved multiple feedstocks derived from both dedicated and secondary sources. Many studies do not provide a comprehensive LCA assessment, often lacking detail on decisions taken, omitting key parts of the value chain, using generic data without uncertainty analyses, or omitting important impact categories. Only 28% of studies included some level of primary data, while 39% of studies did not undertake an uncertainty or sensitivity analysis. Just 8% of studies included data related to dLUC with a further 8% including iLUC, and only 14% of studies considering product end of life within their scope. The authors recommend more transparency in biorefinery LCA, with justification of key methodological decisions. A full value-chain approach should be adopted, to fully assess burdens and opportunities for biogenic carbon storage. We also propose a more prospective approach, taking into account future use of renewable energy sources, and opportunities for increasing circularity within bio-based value chains.

The potential of emerging bio-based products to reduce environmental impacts

The current debate on the sustainability of bio-based products questions the environmental benefits of replacing fossil- by bio-resources. Here, we analyze the environmental trade-offs of 98 emerging bio-based materials compared to their fossil counterparts, reported in 130 studies. Although greenhouse gas life cycle emissions for emerging bio-based products are on average 45% lower (-52 to -37%; 95% confidence interval), we found a large variation between individual bio-based products with none of them reaching net-zero emissions. Grouped in product categories, reductions in greenhouse gas emissions ranged from 19% (-52 to 35%) for bioadhesives to 73% (-84 to -54%) for biorefinery products. In terms of other environmental impacts, we found evidence for an increase in eutrophication (369%; 163 to 737%), indicating that environmental trade-offs should not be overlooked. Our findings imply that the environmental sustainability of bio-based products should be evaluated on an individual product basis and that more radical product developments are required to reach climate-neutral targets.

Production of chemicals and utilities in-house improves the environmental sustainability of phytoplankton-based biorefinery

Life cycle assessment was used to evaluate the environmental impacts of phytoplanktonic biofuels as possible sustainable alternatives to fossil fuels. Three scenarios were examined for converting planktonic biomass into higher-value commodities and energy streams using the alga Scenedesmus sp. and the cyanobacterium Arthrospira sp. as the species of interest. The first scenario (Sc-1) involved the production of biodiesel and glycerol from the planktonic biomass. In the second scenario (Sc-2), biodiesel and glycerol were generated from the planktonic biomass, and biogas was produced from the residual biomass. The process also involved using a catalyst derived from snail shells for biodiesel production. The third scenario (Sc-3) was similar to Sc-2 but converted CO2 from the biogas upgrading to methanol, which was then used in synthesizing biodiesel. The results indicated that Sc-2 and Sc-3 had a reduced potential (up to 60 % less) for damaging human health compared to Sc-1. Sc-2 and Sc-3 had up to 61 % less environmental impact than Sc-1. Sc-2 and Sc-3 reduced the total cumulative exergy demand by up to 44 % compared to Sc-1. In conclusion, producing chemicals and utilities within the biorefinery could significantly improve environmental sustainability, reduce waste, and diversify revenue streams.

Design of biorefineries towards carbon neutrality: A critical review

The increase in worldwide demand for energy is driven by the rapid increase in population and exponential economic development. This resulted in the fast depletion of fossil fuel supplies and unprecedented levels of greenhouse gas in the atmosphere. To valorize biomass into different bioproducts, one of the popular and carbon-neutral alternatives is biorefineries. This system is an appropriate technology in the circular economy model. Various research highlighted the role of biorefineries as a centerpiece in the carbon-neutral ecosystem of technologies of the circular economy model. To fully realize this, various improvements and challenges need to be addressed. This paper presents a critical and timely review of the challenges and future direction of biorefineries as an alternative carbon-neutral energy source.

Multi-feedstock biorefinery concept: Valorization of winery wastes by engineered yeast

The wine industry produces significant amounts of by-products and residues that are not properly managed, posing an environmental problem. Grape must surplus, vine shoots, and wine lees have the potential to be used as renewable resources for the production of energy and chemicals. Metabolic engineering efforts have established Saccharomyces cerevisiae as an efficient microbial cell factory for biorefineries. Current biorefineries designed for producing multiple products often rely on just one feedstock, but the bioeconomy would clearly benefit if these biorefineries could efficiently convert multiple feedstocks. Moreover, to reduce the environmental impact of fossil fuel consumption and maximize production economics, a biorefinery should be capable to supplement the manufacture of biofuel with the production of high-value products. This study proposes an integrated approach for the valorization of diverse wastes resulting from winemaking processes through the biosynthesis of xylitol and ethanol. Using genetically modified S. cerevisiae strains, the xylose-rich hemicellulosic fraction of hydrothermally pretreated vine shoots was converted into xylitol, and the cellulosic fraction was used to produce bioethanol. In addition, grape must, enriched in sugars, was efficiently used as a low-cost source for yeast propagation. The production of xylitol was optimized, in a Simultaneous Saccharification and Fermentation process configuration, by adjusting the inoculum size and enzyme loading. Furthermore, a yeast strain displaying cellulases in the cell surface was applied for the production of bioethanol from the glucan-rich cellulosic. With the addition of grape must and/or wine lees, high ethanol concentrations were reached, which are crucial for the economic feasibility of distillation. This integrated multi-feedstock valorization provides a synergistic alternative for converting a range of winery wastes and by-products into biofuel and an added-value chemical while decreasing waste released to the environment.

Environmental and socio-economic impacts of new plant breeding technologies: A case study of root chicory for inulin production

In Europe, root chicory and other plants are cultivated for their prebiotic food fiber, inulin, which boosts the growth of beneficial gut bacteria and stimulates the human immune system. CHIC, a H2020 project, develops new chicory variants which produce more and reported to be healthier inulin as well as medicinal terpenes. This paper presents an environmental and socio-economic assessment of the whole value chain of the new chicory variants and their derived products using a case study based in the Netherlands. Two scenarios based on new chicory variants using new plant breeding technologies (NPBT) are analyzed and impacts thereof are compared to the reference scenario; the current commercial inulin process from conventional chicory. Both scenarios show higher inulin content, but the inulin adsorption process differs. While one aims to optimize inulin yield, the other one explores the potential of a multipurpose use, yielding inulin and health beneficial terpenes. Methodologically, we employ multi-regional input-output (MRIO) analysis to estimate additional economic benefits, added value and job creation, while by means of life cycle assessment (LCA) effects on greenhouse gas (GHG) emissions and primary energy demand are derived. Both methods, MRIO and LCA, are well suited to analyze the raised issues and draw on the same data. Generally, the results highlight the importance of inulin production at a national and EU-level in the reference scenario. In case of the two scenarios, we find that the related socio-economic impacts are much higher than in the reference scenario and thus highlight their ability to boost economic activity and increase competiveness of the EU, i.e. over 80% of the generated value added stays in the EU. In terms of environmental impacts, the two scenarios show lower GHG emissions and primary energy demand due to the higher efficiencies of the process in the scenarios compared to the reference inulin process. Additionally, regarding the goal of climate neutral production, we find that the majority of GHG emissions stem from the electricity mix and natural gas demand. Replacing these sources of energy with more renewable ones will contribute to this goal.

Safflower-based biorefinery producing a broad spectrum of biofuels and biochemicals: A life cycle assessment perspective

Global environmental awareness has encouraged further research towards biofuel production and consumption. Despite the favorable properties of biofuels, the sustainability of their conventional production pathways from agricultural feedstocks has been questioned. Therefore, the use of non-food feedstocks as a promising approach to ensure sustainable biofuel production is encouraged. However, the use of synthetic solvents/chemicals and energy carriers during biofuel production and the consequent adverse environmental effects are still challenging. On the other hand, biofuel production is also associated with generating large volumes of waste and wastewater. Accordingly, the circular bioeconomy as an innovative approach to ensure complete valorization of feedstocks and generated waste streams under the biorefinery scheme is proposed. In line with that, the current study aims to assess the environmental sustainability of bioethanol production in a safflower-based biorefinery using the life cycle assessment framework. Based on the obtained results, safflower production and its processing into 1 MJ bioethanol under the safflower-based biorefinery led to damage of 2.23E-07 disability-adjusted life years (DALY), 2.35E-02 potentially disappeared fraction (PDF)*m²*yr, 4.76E-01 kg CO₂ eq., and 3.82 MJ primary on the human health, ecosystem quality, climate change, and resources, respectively. Moreover, it was revealed that despite adverse environmental effects associated with safflower production and processing, the substitution of conventional products, i.e., products that are the typical products in the market without having environmental criteria, with their bio-counterparts, i.e., products produced in the biorefinery based on environmental criteria could overshadow the unfavorable effects and substantially enhance the overall sustainability of the biorefinery system. The developed safflower-based biorefinery led to seven- and two-time reduction in damage to the ecosystem quality and resources damage categories, respectively. The reductions in damage to human health and climate change were also found to be 52% and 24%, respectively. The weighted environmental impacts of the safflower-based biorefinery decreased by 64% due to the production of bioproducts, mainly biodiesel and biogas, replacing their fossil-based counterparts, i.e., diesel and natural gas, respectively. Finally, although the main focus of the developed safflower-based biorefinery was biofuel production, waste valorization and mainly animal feed played a significant role in improving the associated environmental impacts.

Integrated biorefinery development using winery waste streams for the production of bacterial cellulose, succinic acid and value-added fractions

An integrated biorefinery has been developed using winery wastes (grape pomace-GP, stalks-GS, wine lees-WL). Bacterial cellulose was produced from GP extracted free sugars. Grape-seed oil and polyphenols were extracted from GP. Experimental design was employed to optimize lignin removal (50.8%) from mixtures of remaining GP solids and GS via NaOH (1.19% w/v) treatment at 70°C for 30 min. Delignification liquid contained condensed tannins with 76% Stiasny number. Enzymatic hydrolysis produced a sugar-rich hydrolysate (40.2 g/L sugars). Ethanol, antioxidants, tartaric acid and nutrient-rich hydrolysate were produced from WL. The crude hydrolysates were used in fed-batch Actinobacillus succinogenes cultures for 37.2 g/L succinic acid production. The biorefinery produces 42.65 g bacterial cellulose, 24.3 g oil, 40.3 g phenolic-rich extract with 1.41 Antioxidant Activity Index, 80.2 g ethanol, 624.8 g crude tannin extract, 20.03 g tartaric acid and 157.8 g succinic acid from 1 kg of each waste stream.

Enhanced conversion of biomass to furfurylamine with high productivity by tandem catalysis with sulfonated perlite and ω-transaminase whole-cell biocatalyst

Production of bio-based chemicals from renewable bioresource is a key driver for moving towards sustainable industry. Furfurylamine is known as an important furfural-upgrading product in organic synthesis, as well as monolithic synthetic pharmaceuticals, fibers, additives and polymers. In one-pot manner, biomass was tandemly catalyzed to furfurylamine with sulfonated Sn-PL catalyst and recombinant ω-transaminase biocatalyst. Sn-PL (2.4 wt%) catalyzed bamboo shoot shell, corncob and rice straw (75.0 g/L) to 76.5-113.0 mM furfural at 44.7-58.5 % yield in γ-valerolactone-water (2:8, v:v) at 170 ℃. The obtained biomass slurries containing furfural were biotransformed to furfurylamine at high yield (0.39-0.42 g furfurylamine/g xylan in biomass) with ω-transaminase biocatalyst using isopropylamine (3.0 mol isopropylamine/mol furfural) as amine donor at 35 ℃. Such a chemoenzymatic one-pot process combined the advantages of both solid acids and whole-cells catalysts, which provided an efficient and sustainable approach for preparing an important bio-based furan chemical furfurylamine.

Environmental analysis of bioethanol production strategies from corn stover via enzymatic and nonenzymatic sugar production

Two different technological process configurations for producing bioethanol from corn stover, namely, enzymatic hydrolysis for sugar production followed by fermentation (P1) and nonenzymatic chemical hydrolysis and subsequent fermentation (P2), were analyzed by a rigorous life cycle assessment. Three environmental impact categories (climate change (CC), fossil depletion (FD), and air pollutant (AP)) were estimated for the both process configurations on a system level. The "best-practice" case with a real scenario of the United States of America indicates that P2 is the most promising strategy from the perspectives of CC, FD, and AP. Considerable savings were achieved by P2: 1.34 kg CO₂-eq/gallon of gasoline equivalent (GGE) for CC, 0.12 MJ/GGE for FD, and 0.24-0.94 g particle matters/GGE for AP. The robustness of the environmental impact results was validated by a scenario uncertainty analysis, and its results indicated that the corn stover composition is crucial.

Life cycle and economic assessment of sugarcane bagasse valorization to lactic acid

In this work, detailed life cycle assessment (LCA) and techno-economic analysis (TEA) of a novel lactic acid (LA) production process from sugarcane bagasse is performed, with the objective of identifying process improvement opportunities. Moreover, this is first such study in the Indian context. Experimental data generated at the Vasantdada Sugar Institute (VSI) for upstream processes is combined with ASPEN Plus simulation of the downstream steps for a commercial plant producing 104 tonnes per day of LA. Equipment sizing is performed and costing is done using standard approaches. OpenLCA is used to develop the LCA model and Ecoinvent database is used to quantify life cycle impacts for 1 kg of LA. Different scenarios for the LA plant are studied. Results showed that the pretreatment stage was crucial from both economic and environmental perspectives. The total life cycle climate change impact for production of 1 kg of lactic acid was 4.62 kg CO₂ eq. The product cost of LA was USD 2.9/kg, and a payback time of 6 years was achieved at a selling price of USD 3.21/kg. Scenario analysis has revealed that lactic acid plant annexed to a sugar mill led to significant environmental and economic benefits. Sensitivity analysis has identified opportunities to reduce the life cycle climate change impact to 2.29 kg CO₂ eq. and product cost to USD 1.42/kg through reduced alkali consumption, higher solid loading, and reduced enzyme loading.

Bioethanol Production from Vineyard Waste by Autohydrolysis Pretreatment and Chlorite Delignification via Simultaneous Saccharification and Fermentation

In this paper, the production of a second-generation bioethanol from lignocellulosic vineyard cutting wastes was investigated in order to define the optimal operating conditions of the autohydrolysis pretreatment, chlorite delignification and simultaneous saccharification and fermentation (SSF). The autohydrolysis of vine-shoot wastes resulted in liquors containing mainly a mixture of monosaccharides, degradation products and spent solids (rich in cellulose and lignin), with potential utility in obtaining valuable chemicals and bioethanol. The autohydrolysis of the vine-shoot wastes was carried out at 165 and 180 °C for 10 min residence time, and the resulted solid and liquid phases composition were analysed. The resulted liquid fraction contained hemicellulosic sugars as a mixture of alpha (α) and beta (β) sugar anomers, and secondary by-products. The solid fraction was delignified using the sodium chlorite method for the separation of lignin and easier access of enzymes to the cellulosic sugars, and then, converted to ethanol by the SSF process. The maximum bioethanol production (6%) was obtained by autohydrolysis (165 °C), chlorite delignification and SSF process at 37 °C, 10% solid loading, 72 h. The principal component analysis was used to identify the main parameters that influence the chemical compositions of vine-shoot waste for different varieties.