Sergio Canzana Capareda

End-of-life tires (ELTs) and refuse-derived fuel (RDF) produced from municipal solid waste (MSW) contain recoverable carbon (C), nitrogen (N), and chemical energy. This study evaluated pyrolysis as a resource-routing approach by comparing ELT and RDF under a common 500 °C batch condition. Product yields, elemental routing, energy retention, and downstream utilization potential were assessed across char, liquid, and gas streams. ELT retained 82.6% of feed carbon and 86.2% of feed energy in char and liquid products, whereas RDF retained 62.4% of feed carbon and 44.6% of feed energy in these condensed streams and produced a larger apparent gas fraction. Nitrogen routing also differed markedly: ELT distributed N relatively evenly between char and liquid, while RDF retained 61.3% of its initial N in char despite containing approximately seven times more N per unit mass of prepared feedstock. ELT produced carbon-rich char and an energy-dense liquid requiring upgrading, while RDF showed greater carbon and nitrogen retention in char and generated a predominantly aqueous condensate. Screening against published utilization studies and relevant product criteria identified plausible material, chemical, and energy-recovery pathways. Overall, the findings highlight the importance of feedstock-specific elemental routing and product quality in evaluating resource recovery, providing a practical basis for integrating thermochemical conversion into circular waste-management systems.

Ammonia (NH₃) emissions from concentrated animal feeding operations (CAFOs) are recognized contributors to secondary fine particulate matter (PM_2.5) formation, yet empirically derived secondary PM_2.5 emission factors applicable to livestock operations remain limited. This study investigated NH₃-derived secondary PM_2.5 formation under controlled laboratory conditions using a PTFE flow reactor in which NH₃ was reacted with sulfur dioxide (SO₂) across ammonia-rich NH₃:SO₂ ratios, with and without zero air. The resulting aerosols were characterized using gravimetric analysis, elemental analysis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS), and particle size distribution (PSD) measurements. The recovered particles were dominated by inorganic ammonium–sulfur species, with FTIR and elemental trends indicating sulfite-related intermediates under no-zero-air conditions and more oxidized ammonium–sulfur products under oxygenated conditions. Accounting for both filter-collected and wall-deposited particles, unit particulate emission factors normalized to ammonia input were derived. Size-based apportionment using PSD data indicated that approximately 76.6% of the recovered particulate mass was within the PM_2.5 size range. Scaling the experimentally derived unit emission factors using literature-based ammonia emission rates yielded an estimated secondary PM_2.5 emission factor of 0.351 ± 0.084 g PM_2.5 per animal head per day for cattle feedlots, corresponding to approximately 3–4% of reported total PM_2.5 emissions. Because the experimental system isolates NH₃–SO₂ interactions under idealized conditions and does not represent full atmospheric chemistry, the derived values should be interpreted as screening-level estimates of NH₃-derived secondary PM_2.5 formation potential intended to support comparative air quality assessments of CAFOs rather than direct predictions of ambient PM_2.5 concentrations.

Converting heterogeneous waste streams into stable carbon materials while minimizing environmental risk is an important goal in sustainable waste management. In this study, waste-derived biochars produced at 500 °C from municipal solid waste (MSW), end-of-life rubber tires (RT), and wood waste (WW) were evaluated for long-term carbon stability and short-term soil chemical responses. Carbon stability was assessed using elemental ratios, fixed carbon content, carbon yield, and carbon sequestration efficiency. Biochars derived from MSW and RT showed low H/C and O/C ratios, high fixed carbon contents, and retained approximately one-third of their original feedstock carbon, indicating strong potential for long-term persistence in soil environments. Short-term soil chemical responses were characterized using a controlled soil incubation. Changes in soil chemistry were primarily associated with limited ash dissolution rather than nutrient enrichment. Electrical conductivity increased moderately but remained below salinity thresholds, and exchangeable calcium (Ca) increased consistently across treatments. Soil pH declined slightly in soils amended with MSW and RT biochars, while WW biochar caused minimal change. Micronutrient behavior varied by feedstock. Copper (Cu) and manganese (Mn) generally declined, suggesting immobilization on biochar surfaces, whereas zinc (Zn) decreased in soils amended with MSW and WW biochars but increased with RT biochar due to its inherent Zn content. Trace metal concentrations in all biochars were below international guideline values, although their long-term mobility under field-relevant dynamic conditions remains uncertain. Overall, the results indicate that waste-derived biochars provide chemically stable carbon inputs to soils, with short-term soil chemical responses serving as indicators of environmental compatibility.

With increased worldwide energy demand and carbon dioxide emissions from the use of fossil fuels, severe problems are being experienced in modern times. Energy is one of the most important resources for humankind, and its needs have been drastically increasing due to energy consumption, the rapid depletion of fossil fuels, and environmental crises. Therefore, it is important to identify and search for an alternative to fossil fuels that provides energy in a reliable, constant, and sustainable way that could use available energy sources efficiently for alternative renewable sources of fuel that are clean, non-toxic, and eco-friendly. In this way, there is a dire need to develop technologies for biofuel production with a focus on economic feasibility, sustainability, and renewability. Several technologies, such as biological and thermochemical approaches, are derived from abundant renewable biological sources, such as biomass and agricultural waste, using advanced conversion technologies for biofuel production. Biofuels are non-toxic, biodegradable, and recognized as an important sustainable greener energy source to conventional fossil fuels with lower carbon emissions, combat air pollution, empower rural communities, and increase economic growth and energy supply. The purpose of this review is to explain the basic aspects of biofuels and their sustainability criteria, with a particular focus on conversion technologies for biofuel production, challenges, and future perspectives.

As a result of the depletion of fossil resources, ongoing population growth, and the industrialized economy, energy demand has been rising quickly throughout the world. India is now the world’s third-largest oil consumer, surpassing Japan and Russia. Today, biofuel research is conducted worldwide because surrounding two essential characteristics: sustainability and renewability. Biofuels have gained considerable significance as a result of dwindling oil sources, worries about energy security, and the escalating environmental issues associated with climate change and greenhouse gas emissions. In most cases, biofuels are produced by subjecting materials that have been densified to the process of heat conversion. In the disciplines of research and development, alternative energy development is a top focus. Due to the depletion of fossil fuel resources, it has become important to find innovative replacements for fossil fuels, such as biofuels, to generate heat and power. Biofuels may be generated using several methodologies, encompassing biological, chemical, and physical approaches. The three steps of densification systems’ pre-, during-, and post-pelletization procedures convert biomass into pellets. Several agricultural wastes, such as grain dust, crop leftovers, and fruit tree residues, are available as sources of agricultural energy. Bioenergy from biomass, such as leftovers and energy crops, can be used to produce contemporary energy carriers. This article focuses on an overview of sustainable and renewable biofuel resources and their commercialization.

LEARNING OBJECTIVES

LEARNING OBJECTIVES

LEARNING OBJECTIVES

LEARNING OBJECTIVES

LEARNING OBJECTIVES