Effective Carbon Dioxide Mitigation and Improvement of Compost Nutrients with the Use of Composts' Biochar.

Composting is a process that emits environmentally harmful gases: CO2, CO, H2S, and NH3, negatively affecting the quality of mature compost. The addition of biochar to the compost can significantly reduce emissions. For effective CO2 removal, high doses of biochar (up to 20%) are often recommended. Nevertheless, as the production efficiency of biochar is low-up to 90% mass loss-there is a need for research into the effectiveness of lower doses. In this study, laboratory experiments were conducted to observe the gaseous emissions during the first 10 days of composting with biochars obtained from mature composts. Biochars were produced at 550, 600, and 650 °C, and tested with different doses of 0, 3, 6, 9, 12, and 15% per dry matter (d.m.) in composting mixtures, at three incubation temperatures (50, 60, and 70 °C). CO2, CO, H2S, and NH3 emissions were measured daily. The results showed that the biochars effectively mitigate CO2 emissions during the intensive phase of composting. Even 3-6% d.m. of compost biochars can reduce up to 50% of the total measured gas emissions (the best treatment was B650 at 60 °C) and significantly increase the content of macronutrients. This study confirmed that even low doses of compost biochars have the potential for enhancing the composting process and improving the quality of the material quality.

Heracleum sosnowskyi pyrolysis - Energy and environmental aspects of biochar utilization.

The Heracleum sosnowskyi is a highly invasive plant species known for its rapid spread and the significant threat it poses to the ecosystem and human health, primarily due to its furanocoumarin content. In the present study, for the first time the pyrolysis process (200-600 °C) of Heracleum was conducted, demonstrating its efficacy in utilizing the material as feedstock and generating valuable solid by-products. It was found that biochar produced at temperatures of 200-300 °C is suitable for solid fuel production (HHV 20.2-24.1 MJ·kg-1) and has strong hydrophobic properties, while pyrolysis over 400 °C promotes the improvement of fertilizing properties by increasing the content of micro and macronutrients (K=112.4 g·kg-1 at 600 °C). The mass and energy analysis proved that in specific conditions (for dry > 300 °C; for wet > 400 °C), pyrolysis can be an effective way for Heracleum biomass conversion into valuable biochar without the need for external energy.

Biochar and Organic Fertilizer Co-Application Enhances Soil Carbon Priming, Increasing CO2 Fluxes in Two Contrasting Arable Soils.

Biochar soil amendments, along with non-tillage agriculture, are often proposed as a strategy for carbon sequestration. It is still questionable how the quality of biochar might influence the priming effect on soil organic matter and whether the addition of unprocessed organic amendments will affect biochar stability. In the study, six different biochars and three exogenous organic matter sources were added to two distinct arable soils. CO2 emission was monitored for 100 days of incubation and CO2 flux was estimated. Results showed that biochar increased soil CO2 fluxes. The highest peaks, up to 162 µg C-CO2 h-1 100 g-1, were recorded in treatments with food waste biochars, suggesting that they serve as a source of easily available carbon to soil microbes. Co-application of raw organic materials (manure and fresh clover biomass) enhanced CO2 emission and carbon losses, especially in sandy soil, where 0.85-1.1% of total carbon was lost in the short-term experiment. Biochar properties and content of labile C can stimulate CO2 emission; however, in a long-term period, this contribution is negligible. The findings of our study showed that more attention should be paid to priming effects caused by the addition of exogenous organic matter when applied to biochar-amended soils.

Deashed Wheat-Straw Biochar as a Potential Superabsorbent for Pesticides.

Biochar activation methods have attracted extensive attention due to their great role in improving sorptive properties of carbon-based materials. As a result, chemically modified biochars gained application potential in the purification of soil and water from xenobiotics. This paper describes changes in selected physicochemical properties of high-temperature wheat-straw biochar (BC) upon its deashing. On the pristine and chemically activated biochar (BCd) retention of five pesticides of endocrine disrupting activity (carbaryl, carbofuran, 2,4-D, MCPA and metolachlor) was studied. Deashing resulted in increased sorbent aromaticity and abundance in surface hydroxyl groups. BCd exhibited more developed meso- and microporosity and nearly triple the surface area of BC. Hydrophobic pesticides (metolachlor and carbamates) displayed comparably high (88-98%) and irreversible adsorption on both BCs, due to the pore filling, whereas the hydrophilic and ionic phenoxyacetic acids were weakly and reversibly sorbed on BC (7.3 and 39% of 2,4-D and MCPA dose introduced). Their removal from solution and hence retention on the deashed biochar was nearly total, due to the increased sorbent surface area and interactions of the agrochemicals with unclogged OH groups. The modified biochar has the potential to serve as a superabsorbent, immobilizing organic pollutant of diverse hydrophobicity from water and soil solution.

Assessing the Influence of Compost and Biochar Amendments on the Mobility and Uptake of Heavy Metals by Green Leafy Vegetables.

Municipal green-waste compost and wheat straw biochar amendments were assessed for their assistance in regulating the mobility of Cu, Pb, Zn, Cd, Cr and Ni and the uptake of these metals by five commonly grown green leafy vegetables (radish, lettuce, dill, spinach and parsley). The amendments were applied alone or combination of both in 5% and 10% (v/w) doses to soil contaminated with heavy metals. Vegetables were grown for eight weeks under greenhouse conditions, and in collected samples plant uptake and metal speciation in soil after sequential extraction procedure (BCR) were analyzed by Microwave Plasma Atomic Emission Spectrometer (MP-AES). The results of our study show that organic amendments noticeably reduced the uptake of heavy metals by various leafy vegetables, with the best result of reduced leaf accumulation for single biochar and biochar-compost mix application at higher dose. Single application of green-waste municipal compost may have adverse effects on heavy metal uptake, increasing the risk of vegetable contamination with Zn, Pb and Cr. This study recommends careful selection of vegetables for cultivation when organic fertilizers are applied to soil with elevated contents of trace elements or co-application of compost in mix with biochar to mitigate possible negative effects and human health risk.

The contribution of water extractable forms of plant nutrients to evaluate MSW compost maturity: a case study.

The object of the experiment was to evaluate municipal solid waste (MSW) compost. Composting was carried out in a pile under aerobic conditions. Total content as well as water-extractable forms of macro and microelements were analysed during composting. Nutrient solubility indices were calculated for samples taken at various stages of maturity. The soluble forms of C, P, K, Ca and Mg decreased relatively to their total forms following maturation phases. For all micronutrients tested, a significant reduction in the proportion of soluble forms in relation to their total content was observed with an increase in composting time. In mature compost, low solubility were found for nitrogen, potassium, sodium and magnesium, which may indicate that the final product is a good source of these nutrients. The solubility index (percentage share of water-extractable forms of macro- and micronutrients in the total content) for iron indicates that the composting process does not affect its degree of solubility. Solubility index instead of the content of water-extractable forms of chosen macro- and microelements could be taken into account in determining the degree of MSW compost maturity.