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Featured Application: obtention of biofuels and platform molecules from agricultural waste. Pea pod cultivation spans various regions and climates, with a global production of around 20 million tons. The pea peel wastes, which make up 30–40% of the total weight of the peas, are freely available in large quantities. The biomass used was characterized via ultimate, proximate, and structural analysis, obtaining 20.2%w of cellulose and 17.4%w of hemicellulose, which, via valorization processes, can be transformed into platform chemicals. Hydrothermal valorization presents itself as a clean form of treatment for these wastes, ranging from 120 to 180 °C (LHW) and from 180 to 260 °C (HTC). The use of LHW can lead to the production of sugars (up to 70%w yield) and levulinic acid (4%w yield), while the use of HTC leads to formic acid (40%w yield) and levulinic acid (4%w yield). The use of LHW for longer periods favors the production of HMF and furfural. The use of homogeneous catalysts (H2SO4, CH3COOH, KOH, and NaHCO3) was implemented, and their selectivity was described. Solid fractions of LHW and HTC were characterized via FTIR and elemental analysis, and the change in their structure was described as they shifted from biomass to biochar. Optimal conditions for each platform chemical were reported to best utilize the pea pod waste. [ABSTRACT FROM AUTHOR]

In this study, we report an efficient, stable, and renewable N, P co-doped coffee biochar-based catalyst loaded with highly dispersed Ni-N x species (Ni/NPCB-600), and it was successfully applied to the aqueous-phase chemoselective reduction or reductive amination of diverse nitroarenes (Yield up to >91%). Experimental and characterization studies revealed that N, P co-doping have a synergistic effect on improving the catalytic performance of Ni/NPCB-600. The textural properties of Ni/NPCB-600 are enhanced after doping of P, which can facilitate mass transfer and expose more accessible active sites in the reaction. The doping of N could induce the formation of Ni-N x sites and enhance the basicity of the Ni/NPCB-600 catalyst, which can promote the adsorption and activation of formic acid and nitroarenes, respectively. This is the first example of N, P co-doped coffee biochar-based catalyst for nitroarenes reduction or reductive amination, and reveals its potential industrial application prospects. [Display omitted] • Ni-N x supported on N, P co-doped coffee biochar was fabricated for the first time. • N, P co-doping could promote the catalytic performance of Ni/NPCB-600. • Using formic acid as a green and renewable source of hydrogen. • Ni/NPCB-600 exhibits good applicability to various nitroarenes. • High activity and chemoselective retained over 10 recycles. [ABSTRACT FROM AUTHOR]

[Display omitted] Fe, N atoms deposited on porous biochar (Fe-N@BC) composites were synthesized and employed as an efficient catalyst for organic pollutant removal and CrVI reduction. Naturally abundant, renewable and N -rich pomelo peel as a carbon and nitrogen source and unsubstituted phthalocyanine/iron phthalocyanine complexes as a Fe and nitrogen resource were used to develop the Fe-N@BC via a carbonization process. It is found that Fe-N@BC hybrids have homogeneous dispersion of Fe and N atoms on 3D hierarchically porous biochar, which significantly improves the performance toward the detoxification of organic pollutants using peroxymonosulfate as an oxidant, as well as the reduction of hexavalent chromium by formic acid as a reductant. Furthermore, the effects of Fe loading and pyrolytic temperature on catalysis were comprehensively analyzed and optimized. The excellent activity of Fe-N@BC in acid media can be attributed to the high dispersion of Fe species, high content of doped nitrogen as well as hierarchical micro-mesopores, which induce to expose more active sites for catalysis. Owing to the structure-enabled acidic stability, Fe-N@BC efficiently retains its activity as well as its structural stability after several cycles of reactions. This work provides a new approach to construct Fe, N -doped biochar as an effective catalyst for the detoxification of organic and inorganic pollutants. [ABSTRACT FROM AUTHOR]

Pyrolysis of calcium-rich feedstock (e.g., poultry manure) generates semi-crystalline and crystalline phosphorus (P) species, compromising its short-term availability to plants. However, enriching poultry manure with magnesium (Mg) before pyrolysis may improve the ability of biochar to supply P. This study investigated how increasing the Mg/Ca ratio and pyrolysis temperature of poultry manure affected its P availability and speciation. Mg enrichment by ∼2.1% increased P availability (extracted using 2% citric and formic acid) by 20% in Mg-biochar at pyrolysis temperatures up to 600 °C. Linear combination fitting of P K-edge XANES of biochar, and Mg/Ca stoichiometry, indicate that P species, mainly Ca–P and Mg–P, are altered after pyrolysis. At 300 °C, adding Mg as magnesium hydroxide [Mg(OH) 2 ] created MgNH 4 PO 4 (18%) and Mg 3 (PO 4) 2.8H 2 O (23%) in the biochar, while without addition of Mg Ca 3 (PO 4) 2 (11%) predominated, both differing only for pyrophosphate, 33 and 16%, respectively. Similarly, the P L 2,3 edge XANES data of biochar made with Mg were indicative of either MgHPO 4.3H 2 O or Mg 3 (PO 4) 2.8H 2 O, in comparison to CaHPO 4.2H 2 O or Ca 3 (PO 4) 2 without Mg. More importantly, hydroxyapatite [Ca 5 (PO 4) 3 (OH)] was not identified with Mg additions, while it was abundant in biochars produced without Mg both at 600 (12%) and 700 °C (32%). The presence of Mg formed Mg–P minerals that could enhance P mobility in soil more than Ca–P, and may have resulted in greater P availability in Mg-enriched biochars. Thus, a relatively low Mg enrichment can be an approach for designing and optimize biochar as a P fertilizer from P-rich excreta, with the potential to improve P availability and contribute to the sustainable use of organic residues. [Display omitted] • Phosphorus bioavailability increases in Mg-enriched biochar up to high pyrolysis temperatures. • OH− anions provided with Mg(OH) 2 could be a mechanism by which Mg-doped biochars have higher P availability. • Adding Mg to poultry manure decreased the formation of Ca–P minerals in low temperatures. [ABSTRACT FROM AUTHOR]

The in-field burning of sugarcane leaf residues presents a major environmental and health burden in Thailand. In this study, sugarcane leaves were converted into a biochar-based slow release phosphorus (P) fertilizer via pyrolysis at 600 °C, and the influence of pre- and post-pyrolysis treatment on the P loading and release was investigated. The sugarcane leaves were pre-treated with an alkaline (diammonium phosphate, DAP) or an acidic P source (phosphoric acid, PA), with or without addition of MgO. Additionally, the biochar was post-treated with DAP to increase the P loading. Extraction of P in DI water and 2% formic acid were used as indicators for potential slow release. The microporous biochars had a specific surface area of 69–333 m2 g−1 and pre-treatment resulted in a P content of 34–82 g kg−1. When MgO was included in the pre-treatment, XRD analysis confirmed formation of crystalline Mg 2 P 2 O 7 , irrespective of the P source. This Mg 2 P 2 O 7 was responsible for slow P release in DI water over 240 h via a dissolution-controlled process. Post-treatment with DAP increased the P loading to 156 g kg−1 in the form of water-soluble monoammonium phosphate (MAP), which did not contribute to slow release. The tunable P release via combinations of pre- and post-pyrolysis treatment makes these engineered biochars attractive as P sources for crops and presents an attractive solution to mitigate in-field sugarcane residue burning. [Display omitted] • P-loaded biochar was prepared by co-pyrolysis of sugarcane leaves with P + MgO. • Addition of MgO in pre-pyrolysis treatment results in slow release of P. • The slow P release is controlled by dissolution of Mg 2 P 2 O 7. • Post-treatment with DAP increases water-soluble P but not slow-release P. [ABSTRACT FROM AUTHOR]

Rice husk biochar (RHB) and phosphate rock (PR) are locally accessible resources that poor farmers in Sub-Saharan Africa (SSA) can utilize to increase rice productivity. However, biochars are variable depending on feedstock, pyrolysis temperature, and duration. Phosphate rocks from SSA are of low solubility. The goal of this study was to determine whether pyrolysis of rice husk (RH), calcination of PR, and the calcination/pyrolysis of a RHB-PR mixture at 300 °C, 500 °C, and 700 °C can increase formic acid (FA)- extractable phosphorous (P). The properties of these RHBs were compared to the properties of RHB produced through a simple farmer-friendly pyrolysis technique termed "Kun-tan". Properties of calcinated PR were also compared to the raw PR. Quartz formed from amorphous SiO2 during RH pyrolysis and was the dominant mineral phase in the biochars, irrespective of the pyrolysis temperature. Formic acid-extractable P content, pH, and ash content of the biochars increased with increasing pyrolysis temperature. At 700 °C, FA-extractable P content of the RHB was 219% more than the feedstock. Hydroxyapatite and quartz were the dominant minerals in the PR irrespective of calcination temperature, indicating that hydroxyapatite and quartz were stable to at least 700 °C. Rather, calcination decreased the FA-extractable P content of the PR. [ABSTRACT FROM AUTHOR]