Life-Cycle Greenhouse Gas Emissions and Human Health Trade-Offs of Organic Waste Management Strategies

Abstract

Waste-to-energy systems can play an important role in diverting organic waste from landfills. However, real-world waste management can differ from idealized practices, and emissions driven by microbial communities and complex chemical processes are poorly understood. This study presents a comprehensive life-cycle assessment, using reported and measured data, of competing management alternatives for organic municipal solid waste including landfilling, composting, dry anaerobic digestion (AD) for the production of renewable natural gas (RNG), and dry AD with electricity generation. Landfilling is the most greenhouse gas (GHG)-intensive option, emitting nearly 400 kg CO2e per tonne of organic waste. Composting raw organics resulted in the lowest GHG emissions, at −41 kg CO2e per tonne of waste, while upgrading biogas to RNG after dry AD resulted in −36 to −2 kg CO2e per tonne. Monetizing the results based on social costs of carbon and other air pollutant emissions highlights the importance of ground-level NH3 emissions from composting nitrogen-rich organic waste or post-AD solids. However, better characterization of material-specific NH3 emissions from landfills and land-application of digestate is essential to fully understand the trade-offs between alternatives.

Near-complete depolymerization of polyesters with nano-dispersed enzymes

“…Given their rapid market growth, understanding solid state enzymology can lead to immediate technological impact toward single use plastics. [28][29][30] However, enzymatic modifications of chemically dormant molecules, such as hydrocarbons and/or polyolefins, require synchronization of multiple biocatalytic processes and are slow even under biologically optimized conditions. 31 Without knowing how microbes modify and degrade polyolefins, 15,21,32,33 understanding how embedded enzymes behave will guide protein engineering and the hybrid bio/abio catalysts design for plastic upcycling without generating secondary environmental contamination.…”

“…The programmable degradation overcomes their incompatibility with industrial compost operations, making them viable polyolefin substitutes. [28][29][30] Analysis on the effects of polymer conformation and segmental cooperativity guide the thermal treatment of the polyester to spatially and temporally program degradation, while maintaining latency during processing and storage. The protectants are designed to regulate biocatalysis and stabilize enzymes during common plastic processing.…”

Transitioning Wastewater Treatment Plants toward Circular Economy and Energy Sustainability

“…Moreover, codigestion of FOG in anaerobic digesters would be more cost-effective and environmentally friendly. 57 Food and agricultural wastes also can be valorized using anaerobic digester technology. 58 An estimated 1.6 billion tons of food waste is available worldwide, 56 which can be converted to valuable energy products (biofuels such as biodiesel, bioethanol, and biooil or biocrude) through various thermochemical and biochemical processes.…”

A Glimpse of the World of Volatile Fatty Acids Production and Application: A review

“…Therefore, much of the anaerobic liquid digestate from intensive-scale anaerobic digesters can only be partially used in Chinese farm fields. Besides, the stored digestate will also have some greenhouse gas emissions into the atmosphere which would cause atmosphere pollution [ 240 ].…”