ABSTRACT Anaerobic digestion is applied to organic wastes, yet a substantial fraction of carbon is released as CO 2 because methanogens lack of low potential reducing equivalents. Here we show that heat‐treated residues of algae Chlorella sorokiniana can be repurposed as chlorophyll‐based biophotosensitizers to couple visible light harvesting to CO 2 methanation by Methanosarcina barkeri ( M. barkeri ), providing a route supplying light‐derived reducing power. Under autotrophic conditions with CO 2 as the sole carbon source, residue supplementation enhanced methane formation in a chlorophyll‐dependent manner and yielded 420 µmol L −1 CH 4 at 16 mg L −1 chlorophyll after 7 d, with most of the increase occurring in the first 3 d. The residues retained functional photosystem II centers that supported charge separation and interfacial electron export, increasing the apparent electron transfer rate from 22.21 to 34.41 s −1 and extending the fluorescence lifetime to 1.89 ns under illumination. Methane enhancement was mainly governed by photosystem II‐derived electron generation and cytochrome‐mediated electron entry into methanogens. Membrane‐bound hydrogenases may also contribute to archaeal electron uptake at the interface, while inhibition of photosystem II or cytochrome‐associated electron transfer reduced CH 4 formation by approximately 70%. Illumination hyperpolarized the proton motive force of M. barkeri by 40 mV, consistent with incoming electrons and protons integrated through proton‐coupled electron transfer steps that feed membrane energy‐conserving modules and strengthen methanogenesis. This study demonstrates that discarded algal residues can function as renewable light‐responsive inputs that introduce photogenerated reducing flux into the methanogenic network and redirect carbon flow from CO 2 loss toward methane formation in anaerobic digestion.

Anaerobic digestion is applied to organic wastes, yet a substantial fraction of carbon is released as CO2 because methanogens lack of low potential reducing equivalents. Here we show that heat-treated residues of algae Chlorella sorokiniana can be repurposed as chlorophyll-based biophotosensitizers to couple visible light harvesting to CO2 methanation by Methanosarcina barkeri (M. barkeri), providing a route supplying light-derived reducing power. Under autotrophic conditions with CO2 as the sole carbon source, residue supplementation enhanced methane formation in a chlorophyll-dependent manner and yielded 420 µmol L-1 CH4 at 16 mg L-1 chlorophyll after 7 d, with most of the increase occurring in the first 3 d. The residues retained functional photosystem II centers that supported charge separation and interfacial electron export, increasing the apparent electron transfer rate from 22.21 to 34.41 s-1 and extending the fluorescence lifetime to 1.89 ns under illumination. Methane enhancement was mainly governed by photosystem II-derived electron generation and cytochrome-mediated electron entry into methanogens. Membrane-bound hydrogenases may also contribute to archaeal electron uptake at the interface, while inhibition of photosystem II or cytochrome-associated electron transfer reduced CH4 formation by approximately 70%. Illumination hyperpolarized the proton motive force of M. barkeri by 40 mV, consistent with incoming electrons and protons integrated through proton-coupled electron transfer steps that feed membrane energy-conserving modules and strengthen methanogenesis. This study demonstrates that discarded algal residues can function as renewable light-responsive inputs that introduce photogenerated reducing flux into the methanogenic network and redirect carbon flow from CO2 loss toward methane formation in anaerobic digestion.

Single use petroleum-based plastics result in environmental contamination. However, the collection of food waste as part of municipal solid waste management requires that the organic matter be bagged up to prevent spillage and transmission of diseases, with the consequence of requiring an additional debagging step before anaerobic digestion. Cellulose-based bioplastic bags can be utilised instead for 1) upcycling the cellulose content of agricultural residues, 2) a non-contaminating replacement for petroleum-based plastics, and 3) contributing increased methane yield to anaerobic digestion of the food waste. Herein, it is shown unequivocally that the bioplastic bags can be degraded by microbial activity, within the timeframe of commercial anaerobic digesters, is converted to methane at a similar extent as other celluloses, produce extra biogas of at least 19 %, and be scaled up to a pilot scale of 1000 L. A Life Cycle Assessment comparing the bioplastic with common fossil-fuel plastic bags shows that the proposed alternative is more beneficial for environmental sustainability, with products made in China, Indonesia, Malaysia, and USA from 25 to 72 % of the global warming potential as compared to lowdensity polyethylene or polypropylene. These findings would help promote a zero-waste circular economy if the digestate is used for subsequent fertilization of agriculture while contributing to UN SDGs including Goals 2, 7, 11, and 12. Synopsis: Cellulose-derived bioplastics are proposed as a safe, anaerobically biodegradable, and environmentallyfriendly alternative to petroleum-based plastics in the anaerobic digestion of food waste, a widely-accepted best practice for food waste management to recover resources and promote a circular economy.

Plastic films have accumulated in soil ecosystems over decades of agricultural activities. These films potentially disrupt the soil structure, hinder nutrient cycling, and deteriorate soil quality. However, there is still a substantial knowledge gap in understanding how real-world waste polyethylene films (WPEFs), with varied shapes and sizes, influence soil quality and plant performance in the fields. This study investigated the effects of WPEFs on soil quality, crop growth, and changes in plastic characteristics. In situ soil incubation was conducted for 4 months under natural field conditions, and lettuce (Lactuca sativa) was cultivated during the period. Soils with 0%-2% of WPEFs were analyzed for physicochemical and biological properties, and lettuces from each soil condition were analyzed for growth indicators after harvest. WPEFs were examined for physicochemical changes using FTIR and SEM. After the incubation, the WPEF 2.0 treatment reduced soil bulk density significantly, from 1.03 to 0.77 g/cm(3), and decreased microaggregates (< 500 mu m) from 22.2% to 17.2%. Meanwhile, the urease activity increased by up to 208.5% at WPEF 0.5. Although the major chemical properties remained relatively stable, lettuce growth was suppressed considerably. At WPEF 2.0, shoot height decreased by 45%, whereas total fresh and dry biomass declined by 58% and 46%, respectively. The findings suggest that the reduction in plant growth performance is driven by WPEF-induced changes in soil physical properties, particularly reduced bulk density and disrupted aggregate stability. The combined effects of soil structure and enzymatic imbalances might have contributed to the observed adverse effects on plant growth.

The large amount of food waste generated globally has significant adverse environmental impacts, highlighting the need for a historic resolution to achieve sustainable managment of food waste as well as its circular economy.

The utilization of biochar derived from biomass residue to enhance anaerobic digestion (AD) for bioenergy recovery offers a sustainable approach to advance sustainable energy and mitigate climate change. However, conducting comprehensive research on the optimal conditions for AD experiments with biochar addition poses a challenge due to diverse experimental objectives. Machine learning (ML) has demonstrated its effectiveness in addressing this issue. Therefore, it is essential to provide an overview of current ML-optimized energy recovery processes for biochar-enhanced AD in order to facilitate a more systematic utilization of ML tools. This review comprehensively examines the material and energy flow of biochar preparation and its impact on AD is comprehension reviewed to optimize biochar-enhanced bioenergy recovery from a production process perspective. Specifically, it summarizes the application of the ML techniques, based on artificial intelligence, for predicting biochar yield and properties of biomass residues, as well as their utilization in AD. Overall, this review offers a comprehensive analysis to address the current challenges in biochar utilization and sustainable energy recovery. In future research, it is crucial to tackle the challenges that hinder the implementation of biochar in pilot-scale reactors. It is recommended to further investigate the correlation between the physicochemical properties of biochar and the bioenergy recovery process. Additionally, enhancing the role of ML throughout the entire biochar-enhanced bioenergy recovery process holds promise for achieving economically and environmentally optimized bioenergy recovery efficiency.

Anaerobic digestion technology, effective for sustainable waste management and renewable energy, but challenged by slow reaction rates and low biogas yields, could benefit from advancements in magnetic nanomaterials. This review explores the potential of magnetic nanomaterials, particularly magnetic biochar nanocomposites, to address these challenges by serving as electron conduits and providing essential iron. This review contributes a thorough overview of the application of magnetic nanoparticles loaded into biochar in anaerobic digestion and engages in a comprehensive discussion regarding the synthesis methods and characterization of various magnetic nanoparticles, elucidating their mechanisms of action in both the absence and presence of magnetic fields. Our review underscores the predominance of co-precipitation (53%) and commercially sourced nanoparticles (29%) as the main synthesis methods, with chemical reduction, pyrolysis, and green synthesis pathways less commonly utilized (8%, 5%, and 5%, respectively). Notably, pyrolysis is predominantly employed for synthesizing magnetic biochar nanocomposites, reflecting its prevalence in 100% of cases for this specific application. By offering a critical evaluation of the current state of knowledge and discussing the challenges and future directions for research in this field, this review can help researchers and practitioners better understand the potential of magnetic biochar nanocomposites for enhancing anaerobic digestion performance and ultimately advancing sustainable waste management and renewable energy production. Graphical Abstract

Long-term anaerobic digestion (AD) of food waste often faces challenges, with volatile fatty acid inhibition being a common issue that hinders optimal performance. This research explores the effect of biochar supplementation on long-term AD of food waste characterized by volatile fatty acid inhibition. The findings demonstrate that adding a modest amount of biochar (0.055 g/L) effectively enhances AD under ambient conditions at 29 degrees C. This biochar supplementation reduced volatile fatty acids to a safe level of 1195 mg/L after 36 days, well within the generally accepted safe threshold of 1500 mg/L. This safe threshold is supported by other studies, which indicate that maintaining VFA concentrations below 1500 mg/L minimizes the risk of process inhibition and ensures stable AD operation. Additionally, the normalized specific biogas yield averaged 1.33 +/- 0.45 m3/kg VS, representing a 47.4% improvement over the control AD conducted under identical conditions. After stabilization, the study assessed whether AD could maintain functionality and stability under mesophilic conditions (35 degrees C) without further biochar supplementation, simulating a real-world scenario to test long-term efficacy in industrial-like conditions. This mesophilic postbiochar AD resulted in an additional 31.8% increase in the normalized average specific biogas yield, reaching 1.95 +/- 0.25 m3/kg VS. Biochar increased Methanosaeta methanogens by 30%, enhancing direct interspecies electron transfer and strengthening syntrophic interactions. This shift made aceticlastic methanogens 9 times more prominent, improving acetate oxidation, biogas yield, and overall AD stability. These findings highlight biochar's potential to enhance decentralized biogas facilities, promote sustainable food waste management, and advance the bioeconomy by providing a replicable model for closing the food waste loop.

Increased awareness of environmental issues and climate change leads to a proportional increase in research and development of “greener” technologies pertaining to renewable energy. In order to avoid simply creating more issues in the process of solving an outstanding problem, the implementation of proposed alternatives has to be studied methodically and holistically from a cradle-to-grave perspective. Currently, the United Nations’ Sustainable Development Goals provide guidelines for country-level analysis but many of the indicators may not be applicable for technology-, products-, services- and system-level evaluation. Additionally, there is a lack of comprehensive and easily comparable sustainability assessments that can be applied across the different Sustainable Development Goals as well as a paucity of relevant targets for renewable energy technologies. Life cycle sustainability assessment, an extension to the widely applied life cycle assessment, is presented herein as the frame of reference to objectively provide insight into the potential impacts of prospective production systems, such that the Sustainable Development Goals can be met in a truly sustainable manner. An overview of current literature (>80 studies) on research into renewable energy production technologies in the areas of wind, solar and biomass is provided, with possible areas of life cycle sustainability assessment utilization highlighted and applied comprehensively in relation to the relevant Sustainable Development Goals. It is thus demonstrated that a Life Cycle Perspective in the form of Life Cycle Sustainability Assessments can be utilized to evaluate renewable energy technologies in a manner that truly meets the United Nations’ Sustainable Development Goals, and the relevant methodology applied to products and services as well.

Methanosarcina thermophila bioaugmentation on biochar as the growth support particle has previously been shown to enhance biomethane production of anaerobic digestion of food waste. In this paper, the duration of the beneficial effects is examined by a semi-continuous thermophilic regime starting from pooled digestate from a previous batch digestion. An additional experiment is performed to decouple the solids retention time, mitigating the washout effect and resulting in improved methane yield for 17 days. The second experiment is extended incorporating various permutations of biochar amendment, and the findings suggest that liquid soluble supplements are essential for prolonging the advantages. Experimental and microbiological analyses indicate that the biochar's enhancement is likely due to microbial factors like direct interspecies electron transfer (DIET) or syntrophic interactions, rather than physicochemical mechanisms.

In a linear economy, consumers typically dispose end-of-life products which are eventually incinerated or landfilled. Digital platforms could unlock rich waste reutilization opportunities and economic benefits by connecting the waste producers with potential waste buyers in online marketplaces. While previous studies mostly focus on input-output matching, this study proposes a decision support system that can be incorporated to an online marketplace to optimize the waste trading based on economic considerations. Moreover, the decision support system could facilitate higher level decisions such as capacity planning and incentive design. Based on a case study on Singapore's organic waste streams, the waste trading platform presents economic benefits for agents that sell their waste. Additionally, enforcing waste reutilization targets would require relevant policy support in terms of incentives or levies, where the levies can be implemented as co-payment rate for the agents. For instance, results showed that when the food waste reutilization target is set as 6 t/d, increasing the co-payment rate from 0 to 20% allows the waste trading network to be self-sustaining without external funding. Finally, sensitivity analyses show that collecting more waste records in the database helps in optimizing the investment decisions, preferably when the number of records exceeds 64.

Utilizing digestate as a fertilizer enhances soil nutrient content, improves fertility, and minimizes nutrient runoff, mitigating water pollution risks. This alternative approach replaces commercial fertilizers, thereby reducing their environmental impact and lowering greenhouse gas emissions associated with fertilizer production and landfilling. Herein, this study aimed to evaluate the impact of various soil amendments, including carbon fractions from waste materials (biochar, compost, and cocopeat), and food waste anaerobic digestate application methods on tomato plant growth (Solanum lycopersicum) and soil fertility. The results suggested that incorporating soil amendments (biochar, compost, and cocopeat) into the potting mix alongside digestate application significantly enhances crop yields, with increases ranging from 12.8 to 17.3% compared to treatments without digestate. Moreover, the combination of soil-biochar amendment and digestate application suggested notable improvements in nitrogen levels by 20.3% and phosphorus levels by 14%, surpassing the performance of the those without digestate. Microbial analysis revealed that the soil-biochar amendment significantly enhanced biological nitrification processes, leading to higher nitrogen levels compared to soil-compost and soil-cocopeat amendments, suggesting potential nitrogen availability enhancement within the rhizosphere's ecological system. Chlorophyll content analysis suggested a significant 6.91% increase with biochar and digestate inclusion in the soil, compared to the treatments without digestate. These findings underscore the substantial potential of crop cultivation using soil-biochar amendments in conjunction with organic fertilization through food waste anaerobic digestate, establishing a waste-to-food recycling system.

The increasing amount of food waste and the excessive use of mineral fertilizers have caused detrimental impacts on soil, water, and air quality. Though digestate derived from food waste has been reported to partially replace fertilizer, its efficiency requires further improvement. In this study, the effects of digestate-encapsulated biochar were comprehensively investigated based on growth of an ornamental plant, soil characteristics, nutrient leaching and soil microbiome. Results showed that except for biochar, the tested fertilizers and soil additives, i.e., digestate, compost, commercial fertilizer, digestate-encapsulated biochar had positive effects on plants. Especially, the digestate-encapsulated biochar had the best effectiveness as evidenced by 9-25% increase in chlorophyll content index, fresh weight, leaf area and blossom frequency. For the effects of fertilizers or soil additives on soil characteristics and nutrient retention, the digestate-encapsulated biochar leached least N-nutrients (<8%), while the compost, digestate and mineral fertilizer leached up to 25% N-nutrients. All the treatments had minimal effects on the soil properties of pH and electrical conductivity. According to the microbial analysis, the digestate-encapsulated biochar has the comparable role with compost in improving the soil immune system against pathogen infection. The metagenomics coupling with qPCR analysis suggested that digestate-encapsulated biochar boosted the nitrification process and inhibited the denitrification process. This study provides an extensive understanding into the impacts of the digestate-encapsulated biochar on an ornamental plant and offers practical implications for the choice of sustainable fertilizers or soil additives and food-waste digestate management.

ABSTRACT We examine the effect of campaign financial disclosures on support for Washington State Initiative 1634, a ballot initiative aimed at limiting tax increases on soda. In an experimental setting, we assess the effect of financial disclosures when paired with the actual textual arguments provided to Washington State voters and the effect of financial disclosures when paired with more complementary textual arguments. We find evidence that financial disclosures influence changes in voter support for the tax initiative. Specifically, our findings indicate that disclosing the top financial contributors “for” and “against” the initiative provides decision-relevant information to voters. Thus, policymakers should consider (1) making donor disclosures freely available in voter information guides, (2) eliminating special-interest group techniques that hide the sources of contributions, and (3) erring on the side of caution when constituents seek to remove ballot-related financial reporting requirements.

Algal biomass is a prospective feedstock for the eco-sustainable production of many different products with added value, such as meals, feeds, and fuels. The remaining biomass from the algae can be used as raw material and can be transformed into useful secondary products after the important macromolecules have been removed. By optimizing algal biomass hydrolysate utilizing microbial fermentation, several studies demonstrated the generation of bioenergy (bioalcohol, biogas, and biohydrogen) and biochemicals (organic acids and biopolymers). Since the harvest and maintenance of sustainable algal cultivation incur considerable energy and economical prowess, developing products from algae remains a challenge to be countered in commercial applications. This is a typical bottleneck issue when processing algae for fuels or chemicals at the pilot scale. Implementation of integrated algae biorefinery methods can substantially reduce the cost of production and energy consumption. An algae-based green economy can be financially more viable and utilizable, especially for countries with weaker economies. This review’s goal is to examine the implementation of integrated biorefineries for the recovery of bioproducts generated from algae and potential applications. In this context, the life cycle analysis and business elements of a unified algal biorefinery are also addressed.

Lignocellulosic substrates constitute the largest fraction of biomass available worldwide, with immense opportunity to recover resources in the form of biogas or nutrients through anaerobic digestion and fermentation technologies. Included in the category of materials are the cellulosic fraction of municipal solid waste, agricultural residues like corn stover, rice straw, empty fruit bunches from oil palm, sugarcane bagasse and other stalks, stems, leaves, seed pods, roots and husks from crops; forestry residues, horticultural wastes such as yard trimmings, grass clippings, tree prunings, and nonfood plants like Jatropha, Miscanthus, Camelina, Panicum, and microalgae. The most pertinent obstacle to widespread adoption of these resource recovery techniques is the recalcitrance of the lignin-encrusted cell walls of the biomass, resulting in suboptimal renewable energy recovery. One or more pretreatment strategies are therefore commonly utilized to reduce particle size as well as recalcitrance in order to optimize biogas production. The aim of this chapter is to provide an introduction to the pretreatment of lignocellulosic materials for the enhancement of biogas production, along with the various issues that arise as obstacles in the adoption of various pretreatment techniques, and finally the current state of the art for various lignocellulosic materials encompassing physical, chemical, biological pretreatments, and combinations thereof with accompanying results reported.