Environmental impact assessment of lignocellulosic lactic acid production: Integrated with existing sugar mills

A review on bio-based polymer polylactic acid potential on sustainable food packaging

Poly(lactic acid) (PLA) stands as a compelling alternative to conventional plastic-based packaging, signifying a notable shift toward sustainable material utilization. This comprehensive analysis illuminates the manifold applications of PLA composites within the realm of the food industry, emphasizing its pivotal role in food packaging and preservation. Noteworthy attributes of PLA composites with phenolic active compounds (phenolic acid and aldehyde, terpenes, carotenoid, and so on) include robust antimicrobial and antioxidant properties, significantly enhancing its capability to bolster adherence to stringent food safety standards. The incorporation of microbial and synthetic biopolymers, polysaccharides, oligosaccharides, oils, proteins and peptides to PLA in packaging solutions arises from its inherent non-toxicity and outstanding mechanical as well as thermal resilience. Functioning as a proficient film producer, PLA constructs an ideal preservation environment by merging optical and permeability traits. Esteemed as a pioneer in environmentally mindful packaging, PLA diminishes ecological footprints owing to its innate biodegradability. Primarily, the adoption of PLA extends the shelf life of products and encourages an eco-centric approach, marking a significant stride toward the food industry's embrace of sustainable packaging methodologies.

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Macroalgal biomass as a potential resource for lactic acid fermentation

Lactic acid is an essential platform chemical with various applications in the chemicals, food, pharmaceutical, and cosmetic industries. Currently, the demand for lactic acid is driven by the role of lactic acid as the starting material for the production of bioplastic polylactide. Microbial fermentation for lactic acid production is favored due to the production of enantiomerically pure lactic acid required for polylactide synthesis, as opposed to the racemic mixture obtained via chemical synthesis. The utilization of first-generation feedstock for commercial lactic acid production is challenged by feedstock costs and sustainability issues. Macroalgae are photosynthetic benthic aquatic plants that contribute tremendously towards carbon capture with subsequent carbon-rich biomass production. Macroalgae are commercially cultivated to extract hydrocolloids, and recent studies have focused on applying biomass as a fermentation feedstock. This review provides comprehensive information on the design and development of sustainable and cost-effective, algae-based lactic acid production. The central carbon regulation in lactic acid bacteria and the metabolism of seaweed-derived sugars are described. An exhaustive compilation of lactic acid fermentation of macroalgae hydrolysates revealed that lactic acid bacteria can effectively ferment the mixture of sugars present in the hydrolysate with comparable yields. The environmental impacts and economic prospects of macroalgal lactic acid are analyzed. Valorization of the vast amounts of spent macroalgal biomass residue post hydrocolloid extraction in a biorefinery is a viable strategy for cost-effective lactic acid production.

Advancement of biorefinery-derived platform chemicals from macroalgae: a perspective for bioethanol and lactic acid

The extensive growth of energy and plastic demand has raised concerns over the depletion of fossil fuels. Moreover, the environmental conundrums worldwide integrated with global warming and improper plastic waste management have led to the development of sustainable and environmentally friendly biofuel (bioethanol) and biopolymer (lactic acid, LA) derived from biomass for fossil fuels replacement and biodegradable plastic production, respectively. However, the high production cost of bioethanol and LA had limited its industrial-scale production. This paper has comprehensively reviewed the potential and development of third-generation feedstock for bioethanol and LA production, including significant technological barriers to be overcome for potential commercialization purposes. Then, an insight into the state-of-the-art hydrolysis and fermentation technologies using macroalgae as feedstock is also deliberated in detail. Lastly, the sustainability aspect and perspective of macroalgae biomass are evaluated economically and environmentally using a developed cascading system associated with techno-economic analysis and life cycle assessment, which represent the highlights of this review paper. Furthermore, this review provides a conceivable picture of macroalgae-based bioethanol and lactic acid biorefinery and future research directions that can be served as an important guideline for scientists, policymakers, and industrial players.

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Valorization of municipal organic waste into purified lactic acid

Municipal organic waste (biowaste) consists of food derived starch, protein and sugars, and lignocellulose derived cellulose, hemicellulose, lignin and pectin. Proper management enables nutrient recycling and sustainable production of platform chemicals such as lactic acid (LA). This review gathers the most important information regarding use of biowaste for LA fermentation covering pre-treatment, enzymatic hydrolysis, fermentation and downstream processing to achieve high purity LA. The optimal approach was found to treat the two biowaste fractions separately due to different pre-treatment and enzyme needs for achieving enzymatic hydrolysis and to do continues fermentation to achieve high cell density and high LA productivity up to 12 g/L/h for production of both L and D isomers. The specific productivity was 0.4 to 0.5 h^-1 but with recalcitrant biomass, the enzymatic hydrolysis was rate limiting. Novel purification approaches included reactive distillation and emulsion liquid membrane separation yielding purities sufficient for polylactic acid production.

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.

Lactic acid separation and recovery from fermentation broth by ion-exchange resin: A review

Lactic acid has become one of the most important chemical substances used in various sectors. Its global market demand has significantly increased in recent years, with a CAGR of 18.7% from 2019 to 2025. Fermentation has been considered the preferred method for producing high-purity lactic acid in the industry over chemical synthesis. However, the recovery and separation of lactic acid from microbial fermentation media are relatively complicated and expensive, especially in the process relating to second-generation (2G) lactic acid recovery. This article reviews the development and progress related to lactic acid separation and recovery from fermentation broth. Various aspects are discussed thoroughly, such as the mechanism of lactic acid production through fermentation, the crucial factors that influence the fermentation process, and the separation and recovery process of conventional and advanced lactic acid separation methods. This review's highlight is the recovery of lactic acid by adsorption technique using ion-exchange resins with a brief focus on the potential of in-site separation strategies alongside the important factors that influenced the lactic acid recovery process by ion exchange. Apart from that, other lactic acid separation techniques, such as chemical neutralization, liquid-liquid extraction, membrane separation, and distillation, are also thoroughly reviewed.

Status of Life Cycle Assessment (LCA) in Africa

Life cycle assessment (LCA) has received attention as a tool to evaluate the environmental impacts of products and services. In the last 20 years, research on the topic has increased, and now more than 25,000 articles are related to LCA in scientific journals databases such as the Scopus database; however, the concept is relatively new in Africa, where the number of networks has been highlighted to be very low when compared to the other regions. This paper focuses on a review of life cycle assessments conducted in Africa over the last 20 years. It aims at highlighting the current research gap for African LCA. A total of 199 papers were found for the whole continent; this number is lower than that for both Japan and Germany (more than 400 articles each) and nearly equal to developing countries such as Thailand. Agriculture is the sector which received the most attention, representing 53 articles, followed by electricity and energy (60 articles for the two sectors). South Africa (43), Egypt (23), and Tunisia (19) were the countries where most of the research was conducted. Even if the number of articles related to LCA have increased in recent years, many steps still remain. For example, establishing a specific life cycle inventory (LCI) database for African countries or a targeted ideal life cycle impact assessment (LCIA) method. Several African key sectors could also be assessed further.

Recent Advances on Purification of Lactic Acid

With increasing interest in developing biodegradable polymers to replace fossil-based products globally, lactic acid (LA) has been paid extensive attention due to the high environment-compatibility of its downstream products. The mainstream efforts have been put in developing energy-efficient conversion technologies through biological and chemical routes to synthesize LA. However, to our best knowledge, there is a lack of sufficient attention in developing effective separation technologies with high atom economics for purifying LA and derivatives. In this review, the most recent advances in purifying LA using precipitation, reactive extraction, emulsion liquid membrane, reactive distillation, molecular distillation, and membrane techniques will be discussed critically with respect to the fundamentals, flow scheme, energy efficiency, and equipment. The outcome of this article is to offer insights into implementing more atomic and energy-efficient technologies for upgrading LA.

Advances in catalytic routes for the production of carboxylic acids from biomass: a step forward for sustainable polymers

Polymers are ubiquitously present in our daily life because they can meet a wide range of needs and fields of applications. This success, based on an irresponsible linear consumption of plastics and the access to cheap oil, is creating serious environmental problems. Two lines of actions are needed to cope with them: to adopt a circular consumption of plastics and to produce renewable carbon-neutral monomers. This review analyses the recent advances in the chemocatalytic processes for producing biomass-derived carboxylic acids. These renewable carboxylic acids are involved in the synthesis of relevant general purpose and specialty polyesters and polyamides; some of them are currently derived from oil, while others can become surrogates of petrochemical polymers due to their excellent performance properties. Polyesters and polyamides are very suitable to be depolymerised to other valuable chemicals or to their constituent monomers, what facilitates the circular reutilisation of these monomers. Different types of carboxylic acids have been included in this review: monocarboxylic acids (like glycolic, lactic, hydroxypropanoic, methyl vinyl glycolic, methyl-4-methoxy-2-hydroxybutanoic, 2,5-dihydroxypent-3-enoic, 2,5,6-trihydroxyhex-3-enoic acids, diphenolic, acrylic and δ-amino levulinic acids), dicarboxylic acids (2,5-furandicarboxylic, maleic, succinic, adipic and terephthalic acids) and sugar acids (like gluconic and glucaric acids). The review evaluates the technology status and the advantages and drawbacks of each route in terms of feedstock, reaction pathways, catalysts and economic and environmental evaluation. The prospects and the new research that should be undertaken to overcome the main problems threatening their economic viability or the weaknesses that prevent their commercial implementation have also been underlined.

Sustainable valorization of sugar industry waste: Status, opportunities, and challenges

Sugarcane processing in sugar industry results in generation of vast amounts of wastes, which can be valorized to biofuels and value-added chemicals based on the concept of circular bioeconomy. For successful commercialization, economic and technological bottlenecks must be clearly identified. In this review, the state of the art of various valorization routes are discussed for each waste stream. Subsequently, studies quantifying the environmental impacts and performing techno-economic assessment are reviewed. The scope and bottlenecks involved in the commercialization of these routes are identified and discussed. The review shows that electricity production from bagasse has matured as a technology but the production of value-added chemicals is still lagging. Here, downstream separation and purification are the major hurdles needing technological innovation. Moreover, indirect environmental and human health benefits due to waste valorization are not adequately accounted for. Further, strong trade-offs between economic and environmental performance exist, necessitating systematic and region-specific decision-making framework.

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

Vine shoots are the viticulture residues generated in high quantities after the grapevine pruning. They are lignocellulosic material poorly exploited as feedstock. These wastes are often dumped in the agriculture fields or burnt. Due to their availability and relatively low price, vine shoots are considered as potential feedstock for biochemical conversion into value-added products. In this work, two biorefinery scenarios using vine shoots as feedstock to co-produce chemicals are assessed from an environmental point of view: production of lactic acid, and co-production of lactic acid and furfural. A CHP area was considered to be annexed to the plants to produce heat and electricity for internal use. The Aspen Plus and SimaPro commercial software were used to perform the LCA of the selected scenarios. The assessed scenarios demonstrate significant reductions in climate change, fossil fuel depletion, freshwater ecotoxicity and eutrophication and human toxicity impacts compared to their counterfactual systems.

Comparative Life-Cycle Assessment of Aquifer Thermal Energy Storage Integrated with in Situ Bioremediation of Chlorinated Volatile Organic Compounds

Due to the increasing need for sustainable energy and environmental quality in urban areas, the combination of aquifer thermal energy storage (ATES) and in situ bioremediation (ISB) has drawn much attention as it can deliver an integrated contribution to fulfill both demands. Yet, little is known about the overall environmental impacts of ATES-ISB. Hence, we applied a life-cycle assessment (LCA) to evaluate the environmental performance of ATES-ISB, which is also compared with the conventional heating and cooling system plus ISB alone (CHC + ISB). Energy supply via electricity is revealed as the primary cause of the environmental impacts, contributing 61.26% impacts of ATES-ISB and 72.91% impacts of CHC + ISB. Specifically, electricity is responsible for over 95% of water use, global warming potential, acidification potential, and respiratory inorganics, whereas the production of the biological medium for bioremediation causes more than 85% of the eco- and human toxicity impacts in both cases. The overall environmental impact of ATES-ISB is two times smaller than that of CHC + ISB. Sensitivity analysis confirms the importance of electricity consumption and electron donor production to the environmental impacts in both energy supply and bioremediation. Thus, future studies and practical applications seeking possible optimization of the environmental performances of ATES-ISB are recommended to focus more on these two essential elements, e.g., electricity and electron donor, and their related parameters. With the comprehensive LCA, insight is obtained for better characterizing the crucial factors as well as the relevant direction for future optimization research of the ATES-ISB system.

Lactic acid fermentation of human excreta for agricultural application

Studies show that source separated human excreta have a fertilizing potential with benefits to plant growth and crop yield similar or exceeding that of mineral fertilizers. The main challenges in fertilizing with excreta are pathogens, and an increased risk of eutrophication of water bodies in case of runoff. This review shows that lactic acid fermentation of excreta reduces the amount of pathogens, minimizes the nutrient loss and inhibits the production of malodorous compounds, thus increasing its agricultural value. Pathogens (e.g., Enterobacteriacea, Staphylococcus and Clostridium) can be reduced by 7 log CFUg^-1 during 7-10 days of fermentation. However, more resistant pathogens (e.g. Ascaris) are not always efficiently removed. Direct application of lacto-fermented faeces to agriculture may be constrained by incomplete decomposition, high concentrations of organic acids or insufficient hygienization. Post-treatment by adding biochar, vermi-composting, or thermophilic composting stabilizes and sanitizes the material. Pot and field experiments on soil conditioners obtained via lactic acid fermentation and post treatment steps (composting or biochar addition) demonstrated increased crop yield and growth, as well as improved soil quality, in comparison to unfertilized controls.

Environmental impacts of producing bioethanol and biobased lactic acid from standalone and integrated biorefineries using a consequential and an attributional life cycle assessment approach

This study evaluates the environmental impacts of biorefinery products using consequential (CLCA) and attributional (ALCA) life cycle assessment (LCA) approaches. Within ALCA, economic allocation method was used to distribute impacts among the main products and the coproducts, whereas within the CLCA system expansion was adopted to avoid allocation. The study seeks to answer the questions (i) what is the environmental impacts of process integration?, and (ii) do CLCA and ALCA lead to different conclusions when applied to biorefinery?. Three biorefinery systems were evaluated and compared: a standalone system producing bioethanol from winter wheat-straw (system A), a standalone system producing biobased lactic acid from alfalfa (system B), and an integrated biorefinery system (system C) combining the two standalone systems and producing both bioethanol and lactic acid. The synergy of the integration was the exchange of useful energy necessary for biomass processing in the two standalone systems. The systems were compared against a common reference flow: "1MJ_EtOH+1kg_LA", which was set on the basis of products delivered by the system C. Function of the reference flow was to provide service of both fuel (bioethanol) at 99.9% concentration (wt. basis) and biochemical (biobased lactic acid) in food industries at 90% purity; both products delivered at biorefinery gate. The environmental impacts of interest were global warming potential (GWP₁₀₀), eutrophication potential (EP), non-renewable energy (NRE) use and the agricultural land occupation (ALO). Regardless of the LCA approach adopted, system C performed better in most of the impact categories than both standalone systems. The process wise contribution to the obtained environmental impacts also showed similar impact pattern in both approaches. The study also highlighted that the recirculation of intermediate materials, e.g. C₅ sugar to boost bioethanol yield and that the use of residual streams in the energy conversion were beneficial for optimizing the system performance.

Lactic acid production from submerged fermentation of broken rice using undefined mixed culture

The present work aimed to characterize and optimize the submerged fermentation of broken rice for lactic acid (LA) production using undefined mixed culture from dewatered activated sludge. A microorganism with amylolytic activity, which also produces LA, Lactobacillus amylovorus, was used as a control to assess the extent of mixed culture on LA yield. Three level full factorial designs were performed to optimize and define the influence of fermentation temperature (20-50 °C), gelatinization time (30-60 min) and broken rice concentration in culture medium (40-80 g L^-1) on LA production in pure and undefined mixed culture. LA production in mixed culture (9.76 g L^-1) increased in sixfold respect to pure culture in optimal assessed experimental conditions. The optimal conditions for maximizing LA yield in mixed culture bioprocess were 31 °C temperature, 45 min gelatinization time and 79 g L^-1 broken rice concentration in culture medium. This study demonstrated the positive effect of undefined mixed culture from dewatered activated sludge to produce LA from culture medium formulated with broken rice. In addition, this work establishes the basis for an efficient and low-cost bioprocess to manufacture LA from this booming agro-industrial by-product.