Insights into hydrothermal treatment of biomass blends: Assessing energy yield and ash content for biofuel enhancement.

This study explores the Hydrothermal Carbonization (HTC) treatment of lignocellulosic biomass blends, delving into the influence of several key parameters: temperature, additive nature and dosage, residence time, and biomass composition. Rapeseeds, Pinus radiata sawdust, oat husks, and pressed olive served as the studied biomasses. One hundred twenty-eight experiments were conducted to assess the effects on mass yield (MY), energy yield (EY), higher heating value (HHV), and final ash content (ASH) by a Factorial Experimental Design. The derived model equations demonstrated a robust fit to the experimental data, averaging an R2 exceeding 0.94, affirming their predictive accuracy. The observed energy yield ranged between 65% and 80%, notably with sawdust and olive blends securing EY levels surpassing 70%, while rapeseed blends exhibited the highest HHV at 25 MJ/kg. Temperature emerged as the most influential factor, resulting in an 11% decrease in MY and a substantial 2.20 MJ/kg increase in HHV. Contrastingly, blend composition and additive presence significantly impacted ASH and EY, with all blends exhibiting increased ASH in the presence of additives. Higher initial hemicellulose and aqueous extractive content in raw biomass correlated proportionally with heightened HHV.

Life cycle assessment of alternatives for industrial textile recycling.

The $882 billion textile trade in 2021 poses environmental concerns, highlighting the importance of encouraging a circular economy to attain sustainable textiles. Therefore, policies must prioritize textile recycling, particularly in developing countries, and sharing information throughout the value chain. This research aims to explore the potential environmental benefits of two industrial recycling processes for textile residues versus the traditional waste management and production process through a life cycle assessment applying the ReCiPe method at midpoint and endpoint levels focusing on generating significant data availability and broader assessment than existing literature to support decision making related to recycling systems for textile residues. Results related to the textile residues recycling process to obtain stripes (R1) and replace sawdust, to fill pushing balls, show that it would produce environmental benefits regardless of location in several midpoint categories. Furthermore, regarding the endpoint results, the DALY savings are mainly due to avoiding landfill, while the savings in ecosystem impacts are generated by avoiding landfill and sawdust production. Regarding the recycling process to obtain recycled yarn and fill (R2) net savings in global warming potential are generated if landfill avoidance is considered. Nevertheless, endpoint results show that DALYs of all the avoided processes correspond to 1.5 times the impacts of all the R2 recycling processes, mainly due to avoiding virgin yarn production. Therefore, both recycling processes are recommended. However, some strategies are required to generate greater benefits, such as applying the R2 recycling process as the first option for stretchable textile waste, and after being used, going through the R1 recycling process. In addition, the strategic placement of the R1 recycling facility should be distant from areas of sawdust production. A sensitivity analysis was carried out due to the variability of virgin products to replace in the market.

Market concentration in industrial and commercial non-hazardous waste valorisation: the case of Chile.

Market concentration among buyers of recycled materials is a phenomenon discussed since the 1980 s by the anti-trust literature. Yet, there is still a lack of studies on simultaneous market concentration on both the supply and demand sides. This is particularly relevant when Extended Producer Responsibility (EPR) policies produce two-sided waste generation and valorisation markets. Thus, the purpose of this study is to explore the link between market concentration on the generation side and market share on the valorisation side. Specifically, this research addresses the case of valorisation of commercial and industrial non-hazardous waste in Chile. The analysis covers 261 companies that valorised industrial and commercial non-hazardous waste between 2015 and 2019. Being part of the top 10 % of generator companies in Chile is significantly correlated to higher valorisation market share, in a context in which mean market share per company decreased, total tons valorised stagnated, and the country-level valorisation rate diminished.

Hybrid porous media gasification of urban solid waste pre-treated by hydrothermal carbonization.

Global population growth and rising consumption levels have significantly increased resource use and energy demand, leading to higher greenhouse gas concentrations and increased waste output. As a result, alternative waste treatment methods for sustainable municipal solid waste (MSW) management are crucial. This research evaluates the efficiency of integrating hydrothermal carbonization (HTC) and gasification for an optimized MSW biomass blend. HTC was conducted for one hour at 220°C in a 5 L reactor, followed by gasification in a hybrid porous medium gasifier. The study investigated the effects of different filtration speeds on combustion temperature and hydrogen concentrations. The results showed that a filtration speed of 35 cm/s resulted in a maximum combustion temperature of 1035.7°C. The temperature remained consistent across filter speeds, while higher velocities yielded higher hydrogen concentrations. Additionally, increasing the filtration velocity raised temperatures in the hybrid bed while increasing the volumetric fraction of biomass decreased maximum temperatures. This research contributes to the understanding of merging HTC and gasification for MSW biomass blend treatment, aiming to reduce environmental impacts and costs while promoting renewable resources for long-term energy production.

Corrigendum: A Review of the Use of Linear Programming to Optimize Diets, Nutritiously, Economically and Environmentally.

[This corrects the article DOI: 10.3389/fnut.2018.00048.].

An environmental assessment for municipal organic waste and sludge treated by hydrothermal carbonization.

Climate change is the world's greatest challenge today, the reason why it is urgent to optimize industrial processes and find new renewable energy sources. Hydrothermal carbonization (HTC) is one of the Waste-to-Energy technologies with greater projections due to its operative advantages. However, for its large-scale implementation, there are challenges related to the variability of the composition of the waste biomass and the seasonal and geographical availability. This research applied the Life Cycle Analysis methodology to evaluate the environmental impacts caused by three biomasses blends as raw material in the HTC process at laboratory scale. The blends analyzed considered different organic fractions of municipal solid waste (food and pruning) and sewage sludge. The results showed that blend 1 had a lower environmental impact for the case of production in the experimental laboratory level, compared with blends 2 and 3. This is mainly due to its greater calorific value and mass yield, which allows obtaining more hydrochar compared with the other blends, increasing the energy efficiency of the process. Also, between 87.94% and 98.00% of the energy reduction is required to obtain neutral impacts regarding the energy requirements in the experimental laboratory level scenario and the Chilean energy matrix. The processing of blends in HTC has excellent potential in a context where municipal solid wastes have been disposed in sanitary landfills or dumps, as in most emerging countries. Since this study incorporated data from the literature, future studies should perform an elemental analysis to provide experimental and differentiated data.

Exploring an alternative to the Chilean textile waste: A carbon footprint assessment of a textile recycling process.

Global population growth and rising living standards are increasing apparel consumption. Consequently, the consumption of resources and the generation of textile waste are increasing exponentially. For instance, according to the World Bank, Chile has increased textile imports by 500% in the last 20 years, even though the population has only increased by 26%. This textile import increase has resulted in the clothing desert that has been seen recently in northern Chile because most of the textiles at the end of their useful life will be disposed of in landfills or open dumps. This evidences the urgency of more efficient technologies that reduce the consumption of resources and that value waste on the way to a circular and sustainable economy. Since the textile recycling industry and environmental impact studies are currently in their nascent stages in Chile, the objective of this article is to explore the potential environmental benefits of a textile recycling process and, therefore, the related challenges towards more sustainable options. The considered textile recycling process incorporates mixed waste and is compared with landfills in terms of CO2eq because it represents the conventional treatment of waste and the substitution of products from primary sources. The results show that textile waste landfills emit 423.4 kg CO2eq per ton, while products from primary sources emit an average of 6496.65 kg CO2eq, compared to the textile recycling process that only it emits 1142.12 kg CO2eq per ton, obtaining an average of 5778 kg CO2eq avoided per ton of textile waste, achieving environmental benefits. However, it is necessary to highlight the dependence of this result on the choice of replaced products and the energy matrix. Thus, we assessed the energy matrix, evaluating the positive impact of implementing an energy matrix based on wind or solar energy.

Closing the gap in the municipal solid waste management between metropolitan and regional cities from developing countries: A life cycle assessment approach.

Municipal solid waste (MSW) management is an important challenge in developing and emerging countries, where two realities co-exist. On the one hand, their metropolitan cities exhibit an integrated MSW system with a specialized fleet for the collection and landfills for the final disposal, concentrating on environmental initiatives such as municipal recycling programs. On the other hand, their regional cities show an MSW system based on adapted transports for collection and open dumps for final disposal. Besides, they face other environmental problems due to local conditions. This research proposes a life cycle assessment (LCA) approach to close the gap between these two realities. In particular, we study the city of Valdivia (Chile), one of the main regional capitals of South America, which shares similarities with other southern regional cities in the Global South. This city disposes 95% of its MSW in open dumps and presents one of the highest environmental pollution rates in Latin America. We analyze the greenhouse gas (GHG) emissions and energy performance of six scenarios, seeking a solution for these problems. The results obtained show that a waste-to-energy scenario would generate savings of GHG emission and particulate matter, reaching 11.3% and 21.8%, respectively. Using our LCA approach, we can provide environmental evidence to highlight the importance of improving MSW management in regional cities, closing the gap with MSW management in metropolitan cities, and contributing to national targets such as United Nations Sustainable Development Goals and Nationally-Determined Contributions.