Biomass

The rapid growth of the human population and industrialization has intensified anthropogenic activities, leading to the release of various toxic chemicals into the environment, triggering significant risks to human health and ecosystem stability. One sustainable solution to remove toxic chemicals from various environmental matrices, such as water, air, and soil, is bioremediation, an approach utilizing biological agents. Microalgae, as the primary producers of the aquatic environment, offer a versatile bioremediation platform, where their metabolic processes break down and convert pollutants into less harmful substances, thereby mitigating the negative ecological impact. Besides the CO₂ sequestration potential, microalgae are a source of renewable energy and numerous high-value biomolecules. Additionally, microalgae can mitigate various toxic chemicals through biosorption, bioaccumulation, and biodegradation. These remediation strategies propose a sustainable and eco-friendly approach to address environmental pollution. This review evaluates the microalgal mitigation of major environmental contaminants—heavy metals, pharmaceuticals and personal care products (PPCPs), persistent organic pollutants (POPs), flue gases, microplastics, and nanoplastics—linking specific microalgae removal mechanisms to pollutant-induced cellular responses. Each section explicitly addresses the effects of these pollutants on microalgae, microalgal bioremediation potential, bioaccumulation process, the risks of trophic transfer, and biomagnification in the food web. Herein, we highlight the current status of the microalgae-based bioremediation prospects, pollutant-induced microalgal toxicity, bioaccumulation, and consequential biomagnification. The novelty of this review lies in integrating biomagnification risks with the bioremediation potential of microalgae, providing a comprehensive perspective not yet addressed in the existing literature. Finally, we identify major research gaps and outline prospective strategies to optimize microalgal bioremediation while minimizing the unintended trophic transfer risks.

Agricultural residues such as maize byproducts and discarded cocopeat substrates are abundant but underutilised biomass resources. Improving their fuel quality requires densification, such as pelletisation, combined with thermochemical upgrading. In this study, pellets were prepared by blending cocopeat and maize residues at weight ratios of 9:1, 7:3, and 5:5, followed by torrefaction at 220, 250, and 280 °C. Their fuel characteristics were evaluated through mass yield, elemental and proximate analyses, chemical composition, calorific value, combustion indices, and grindability. Results showed that increasing maize residue content reduced ash and fuel ratio but increased volatile matter, while cocopeat-rich pellets provided higher fixed carbon and lignin contents, improving thermal stability. Torrefaction significantly enhanced calorific value (up to 21.83 MJ/kg) and grindability, while increasing aromaticity. However, higher torrefaction severity decreased the combustibility index but improved volatile ignitability, indicating a trade-off between ignition behaviour and stable combustion. An optimal balance was observed at 250 °C, where energy yield and combustion performance were maximised. This study demonstrates the feasibility of valorising discarded cocopeat substrates, blended with maize residues, into renewable solid fuels, and provides practical guidance for optimising blending ratios and torrefaction conditions in waste-to-energy applications.

The transition to a circular economy requires effective food waste (FW) collection and recycling systems. This study aims to evaluate general public attitudes, behaviours, and systemic challenges related to FW sorting in Latvia, in light of the recent mandate for separate biowaste collection. The study covers two important sections—assessment of the amount of FW generated in primary production sectors, and a pilot case study of biodegradable waste sorting in selected households in Latvia. A mixed-methods approach was used, combining a nationwide survey of 458 entities involved in primary food production and 115 households, followed by 99 households with backyards voluntarily participating in a pilot case study to evaluate their BW management practices. The research findings reveal that there is a need to establish a precise/specific framework for the evaluation of FW for each sector; the development of appropriate coefficients would facilitate the process of estimating waste generated by primary production in the future. Research findings revealed that inhabitants are interested in home composting; however, the implementation of home composting requires active support from project implementers, including increasing environmental awareness and providing financial incentives. These results offer practical insights for municipalities and national stakeholders aiming to increase biowaste collection rates and support country-level broader sustainability goals. The research results have practical application with the possibility to replicate the best practices and recommendations to other countries or regions within the EU and beyond.