Release of essential plant nutrients from manure- and wood-based biochars

Several biochars have a considerable amount of essential plant nutrients; however, the release of those nutrients in soil is not well understood. Therefore, in this study, six biochars with varying nutrient contents were produced from Japanese larch (Larix kaempferi, JL), dairy manure (DM), and chicken manure (CM) at 300 and 500 °C and incubated in a temperate clay loam soil to investigate their nutrient release dynamics. The available N, P, and K release patterns of the biochars (2% dry-basis) were compared with the recommended fertilizer dose of sweet corn (Zea mays convar. saccharata) for 120 days. The results indicated that only chicken manure biochars (C/N ratio < 8) have the potential to satisfy plant needs by releasing sufficient N, P, and K. Fourier-transform infrared analysis revealed that N-containing amide dissolution was the major mechanism behind the 49% N release from the CM300 biochar. A higher production temperature (500 °C) diminished most of these amides, resulting in lower N release from CM500 (8.9%). Nitrification-induced reduction of soil pH caused Ca/Mg-P dissolution from manure biochars and enhanced P release. Much of the released phosphates later became unavailable in the soil by aluminosilicate complex formation. DM biochar also released adequate P and K, and production at 500 °C generally performed better than at 300 °C. Effect of coexisting ions on some nutrient release was found, though was statistically nonsignificant. Overall, results revealed that low-temperature (≤500 °C) CM and DM biochars can become comprehensive or complementary sources of plant nutrients, respectively, with some enhanced nutrient-retaining potential, although inherent soil properties may play a significant role

Synthesizing biochar-based fertilizer with sustained phosphorus and potassium release : Co-pyrolysis of nutrient-rich chicken manure and Ca-bentonite

Biochar-based fertilizers (BBFs) are attracting considerable interest due to their potential to improve soil properties and the nutrient use efficiency of plants. However, a sustainable agricultural system requires decreased dependency on chemical fertilizer for BBF production and further enhancement of the slow-release performance of BBFs. In this study, we propose a simple biochar-based slow-release fertilizer synthesis technique involving the co-pyrolysis of 10 to 25% (w/w) Ca-bentonite with chicken manure as the only nutrient source (N, P, K). To evaluate nutrient release in contrasting soil media, we mixed pristine and modified chicken manure biochars (CMB) with both quartz sand and clay loam soil and compared the release with that of the recommended fertilizer dose for sweet corn (Zea mays convar. saccharata). Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy revealed that Ca-bentonite reduced readily soluble orthophosphates by forming less-soluble Ca/Mg-phosphates. In addition, significantly slower K release in soil (on average ~ 22% slower than pristine CMB) was observed from biochar containing 25% Ca-bentonite, since K is strongly adsorbed in the exchange sites of crystalline bentonite during co-pyrolysis. Decomposable amides were unaltered and thus Ca-bentonite had no significant impact on N release. Comparison of nutrient release in different media indicated that on average P and K release from BBFs in coarse sand respectively was 38% and 24% higher than in clay loam, whereas N release was substantially greater (49%) in the latter, owing to significant microbial decomposition. Overall, Ca-bentonite-incorporated CMBs, without any additional fertilizer, can satisfy plant nutritional needs, and exhibit promising slow-release (P and K) performance. Further process modification is required to improve N-use efficiency after carefully considering the soil components

Effects of Ash Composition and Combustion Temperature on Reduced Particulate Matter Emission by Biomass Carbonization.

Thermochemical pretreatment, including carbonization, has been suggested as a method to reduce particulate matter (PM) emissions during the combustion of biomass. However, the carbonization efficiency might not be equal for all types of biomass because of composition heterogeneity and differences in combustion conditions. Therefore, an assessment of PM emission reduction by carbonization of various types of biomass at different combustion temperatures is required. In this study, seven different types of biomass (larch, poplar, miscanthus, bamboo grass, rice straw, rice husk, and dairy manure) and their biochars (prepared at 400 °C) were combusted at 650, 750, and 850 °C. The results showed that PM emission was reduced as much as 95.45% after carbonization as a result of volatile matter removal. The efficiency of PM reduction was greatest at low combustion temperatures for all feedstocks. Although the combustion temperatures did not strongly affect PM emissions from low-ash (??6.7%) biomass, higher heating temperatures (??750 °C) stimulated PM emissions from ash-rich rice straw and dairy manure biochar. The transformation of minerals in rice straw, rice husk, and dairy manure was also investigated at different combustion temperatures (650, 750, and 850 °C). Mineral analysis revealed that enhanced PM emission from ash-rich biochar samples was attributable to a greater concentration of Na and K, which likely resulted from melting at higher combustion temperatures. We found that carbonization can substantially reduce PM emissions for low-alkali-containing biomass and that a lower combustion temperature of biochar is preferable to suppress PM emissions for high-alkali-containing biomass. Our findings reveal a possible approach to waste-to-energy production with reduced health risks

Effects of Ash Composition and Combustion Temperature on Reduced Particulate Matter Emission by Biomass Carbonization.

Thermochemical pretreatment, including carbonization, has been suggested as a method to reduce particulate matter (PM) emissions during the combustion of biomass. However, the carbonization efficiency might not be equal for all types of biomass because of composition heterogeneity and differences in combustion conditions. Therefore, an assessment of PM emission reduction by carbonization of various types of biomass at different combustion temperatures is required. In this study, seven different types of biomass (larch, poplar, miscanthus, bamboo grass, rice straw, rice husk, and dairy manure) and their biochars (prepared at 400 °C) were combusted at 650, 750, and 850 °C. The results showed that PM emission was reduced as much as 95.45% after carbonization as a result of volatile matter removal. The efficiency of PM reduction was greatest at low combustion temperatures for all feedstocks. Although the combustion temperatures did not strongly affect PM emissions from low-ash (??6.7%) biomass, higher heating temperatures (??750 °C) stimulated PM emissions from ash-rich rice straw and dairy manure biochar. The transformation of minerals in rice straw, rice husk, and dairy manure was also investigated at different combustion temperatures (650, 750, and 850 °C). Mineral analysis revealed that enhanced PM emission from ash-rich biochar samples was attributable to a greater concentration of Na and K, which likely resulted from melting at higher combustion temperatures. We found that carbonization can substantially reduce PM emissions for low-alkali-containing biomass and that a lower combustion temperature of biochar is preferable to suppress PM emissions for high-alkali-containing biomass. Our findings reveal a possible approach to waste-to-energy production with reduced health risks