The increasing demand for renewable energy sources has led to significant interest in second-generation biofuels derived from lignocellulosic biomass and waste materials. This review underscores the pivotal role of lignocellulosic biomass valorization in meeting global energy needs, mitigating greenhouse gas emissions, and fostering a circular bioeconomy. Key pretreatment methods—including steam explosion, pressure treatment, and chemical pretreatment—are analyzed for their ability to enhance the accessibility of cellulose and hemicellulose in enzymatic saccharification. Advances in cellulolytic enzyme development and fermentation strategies, such as the use of genetically engineered microorganisms capable of fermenting both hexoses and pentoses, are discussed in detail. Furthermore, the potential of biorefinery systems is explored, highlighting their capacity to integrate biomass valorization into biofuel production alongside high-value bioproducts. Case studies and recent trends in bioethanol and biogas production are examined, providing insights into the current state of research and its industrial applications. While lignocellulosic biofuels hold considerable promise for sustainable development and emissions reduction, challenges related to cost optimization, process scalability, and technological barriers must be addressed to enable large-scale implementation. This review serves as a comprehensive foundation for bridging the gap between laboratory research and industrial application, emphasizing the need for continued innovation and interdisciplinary collaboration in biofuel technologies.

This study investigated the conversion of kitchen waste into environmentally friendly fertilizers and soil improvers using five various treatments: (1) inoculation with effective microorganisms followed by anaerobic fermentation, (2) 12 days of decay before adding a double dose of effective microbes, (3) sterilization at 70 °C for 1 h after 12 days of decay, and (4) sterilization followed by effective microbes addition. In (5), waste was decayed, sterilized, and digested without effective microbes. For comparison, a commercial NPK fertilizer and pelleted cow manure were also applied. These treatments were tested in a ryegrass growth experiment in a glasshouse under warm conditions in northern Poland, with four successive harvests. Measurements included dry matter yield, N uptake, N utilization per hectare, and soil properties. Results showed that granulated cow manure and (5) were the most effective fertilizers during the first two months, while other kitchen waste treatments performed better in months 3 and 4, functioning as slow-release fertilizers. The relative agronomic effectiveness after four months was 88%, 67.8%, 60.2%, 48.6%, and 48.6% for (5), (4), (2), (3), and (1), respectively, compared to cow manure, and 36.3%, 27.9%, 24.8%, 20%, and 20% compared to NPK fertilizer. The study indicated that using a double dose of effective microbes produced yields comparable to sterilized waste, suggesting that microbial treatments could replace energy-intensive sterilization, reducing costs. Soil properties were largely unaffected, but residual soil N levels increased from 0.5 to 1.1 g/kg.

Leather waste contains up to 10% nitrogen (N); thus, combustion or gasification only for the energy recovery would not be rational, if safety standards are met. On the other hand, the chromium (Cr) content exceeding 5% in half of the waste stream (w/w) is too significant to be applied in agriculture. In this work, four acid hydrolysates from leather waste shavings, both wet-white free of Cr and wet-blue with Cr, were used: two with a mixture of acids and supplemented with Cu, Mn, and Zn, and the other two as semi-products from collagen extraction using hydrochloric acid. Additionally wet-green leather waste shavings, e.g., impregnated with olive extract, were used followed by the two treatments: amendment with a biochar from “wet white” leather waste shavings and amendment with this biochar incubated with the commercial phosphorus stimulating microbial consortia BactoFos. They were applied as organic nitrogen-based fertilizers in a glasshouse experiment, consisting of 4–5 subsequent harvests every 30 days, under spring–autumn conditions in northern Poland. Biochar-amended wet-greens provided the highest nitrogen use efficiencies, exceeding 100% after 4 months of growth (for 20 kg N/ha) and varying from 17% to 37% in particular months. This is backed up by another parameter (relative agronomic effectiveness) that for these materials exceeded 150% for a single month and in total was around 33%. Biochar amendments significantly increased agronomic parameters for wet-greens, and their microbial treatment enhanced them even further. Recycling this type of waste can replace inorganic fertilizers, reducing greenhouse gas emissions and carbon footprint.

The easiest way to utilise leather waste shavings is normally to produce new fuels from the most contaminated fractions for combustion or gasification. But since these waste contain up to 10% of nitrogen (N), burning it only for the energy recovery would not be rational. On the other hand, the chromium (Cr) content exceeding 5% in half of the waste stream (w/w) is too significant to be applied in agriculture. In this work, 4 acid hydrolysates from leather waste shavings both wet-white free of Cr and wet-blue with Cr were used: 2 with a mixture of acids and supplemented with Cu, Mn, Zn and other 2 as semi-product from collagen extraction using hydrochloric acid. The acid hydrolysates were prepared using a specific combination of acids under controlled conditions, ensuring the maximum release of nitrogen while maintaining the safety and integrity of the process. Additionally wet-green leather waste shavings eg. impregnated with olive extract were used followed by their 2 treatments: amendment with a biochar from “wet white” leather waste shavings and amendment with this biochar incubated with a commercial phosphorus stimulating microbial consortia BactoFos. They were applied as organic nitrogen-based fertilisers in a glasshouse experiment, consisting of 4-5 subsequent harvests every 30 days, under spring-autumn conditions in northern Poland. Ryegrass dry matter and nitrogen plant content were measured across 7 increasing fertiliser doses. Nitrogen utilisation, relative agronomic effectiveness, nitrogen use efficiency, total ryegrass dry matter and nitrogen utilisation breakdown across harvests were calculated. Biochar amended wet-greens provided the highest nitrogen use efficiencies exceeding 100% after 4 months growth (for 20 kg N/ha) and varying from 17% to 37% in particular months. This is backed up by another parameter (relative agronomic effectiveness) that for these materials exceeded 150% for single month and in total around 33%. Biochar amendments significantly increased agronomic parameters for wet-greens and their microbial treatment enhanced them even further. In sustainability aspects, assuming only the industrial partner waste potential, that gives 919,8 t of recycled nitrogen per year, which comes back to the environment in plant biomass. Recycling this type of waste can replace inorganic fertilizers reducing greenhouse gas emissions and carbon footprint.

Rapid decompression is a physical route to disrupting lignocellulose, but its gas-based variants operate below 60 bar, release through valves, and have not been documented on the millisecond scale of the pressure drop. We present the design, safety analysis, and cycle energetics of a laboratory reactor in which compressed air at up to 300 bar and up to 90 °C is released through the full chamber bore by a press-clamped lid that lifts when the clamping force is removed. The 1.13 dm³ chamber of 316L steel was assessed with the Lamé solution, thick-plate theory, and the EN 13445-3 and ASME VIII-1 rules and verified by a 320-bar leak test and approximately 150 decompressions. The plain wall has safety factors of 1.9 and 1.5 at 20 and 90 °C, whereas the edges of the Ø11.8 mm ports reach the yield strength at 255–285 bar and should set the allowable pressure. Fifteen wheat-straw decompressions recorded at 1 ms resolution took 84–780 ms (median 177 ms), 100 times longer than the 1.5 ms predicted for the lid opening; the decay corresponds to a throttling area of about 2% of the bore, pointing to the two-phase outflow of the chamber contents as the rate-limiting step. The electrical energy of compression (0.29–0.33 MJ per cycle at 160 bar) exceeds the methane-energy gain by about fourfold (benefit-to-input ratio 0.22–0.26), so at laboratory scale the process is energetically unfavorable; reversing the balance would require a fourfold denser charge or industrial compression efficiency with energy recovery.

Recycled nutrient fertilizers (RNFs) derived from organic and industrial waste streams offer a promising approach to nutrient recovery and sustainable agricultural production. However, their agronomic performance and the potential benefits of enrichment with biologically active, waste-derived materials remain insufficiently understood. This study evaluated two multi-component RNFs, four-ingredient pellets, first with biochar (BADSS) and second with bovine shavings (SADSS), with and without enrichment using chitosan-containing seafood waste, in a four-month greenhouse experiment with ryegrass across nitrogen application rates ranging from 20 to 370 kg N ha⁻¹. Biomass production, nitrogen uptake, agronomic effectiveness (AE), apparent nitrogen recovery (ANR), soil chemical properties, and photosystem II efficiency were assessed. The results demonstrated that fertilizer performance depended strongly on matrix composition and nitrogen application rate. BADSS induced a stronger increase in residual soil pH, whereas SADSS maintained more balanced soil conditions. Chitosan enrichment enhanced long-term nitrogen uptake and biomass production when combined with SADSS, while its effects in the BADSS matrix were less consistent, particularly at excessive nitrogen inputs. Correcting fertilizer performance for additional nitrogen introduced with the chitosan-containing amendment substantially reduced apparent AE and ANR, highlighting the importance of complete nutrient accounting when assessing enriched fertilizers. Overall, the findings indicate that seafood-waste-derived chitosan can improve the agronomic performance of recycled nutrient fertilizers, although its effectiveness depends on the composition of the fertilizer matrix and the applied nitrogen rate. Integrating seafood-processing residues into waste-derived fertilizer systems offers a promising strategy for valorizing underutilized resources, improving nutrient management, and supporting circular bioeconomy approaches to sustainable agriculture.