Modelling the potential for soil carbon sequestration using biochar from sugarcane residues in Brazil.
ABSTRACT: Sugarcane (Saccharum officinarum L.) cultivation leaves behind around 20 t ha-1 of biomass residue after harvest and processing. We investigated the potential for sequestering carbon (C) in soil with these residues by partially converting them into biochar (recalcitrant carbon-rich material). First, we modified the RothC model to allow changes in soil C arising from additions of sugarcane-derived biochar. Second, we evaluated the modified model against published field data, and found satisfactory agreement between observed and predicted soil C accumulation. Third, we used the model to explore the potential for soil C sequestration with sugarcane biochar in São Paulo State, Brazil. The results show a potential increase in soil C stocks by 2.35?±?0.4 t C ha-1 year-1 in sugarcane fields across the State at application rates of 4.2 t biochar ha-1 year-1. Scaling to the total sugarcane area of the State, this would be 50 Mt of CO2 equivalent year-1, which is 31% of the CO2 equivalent emissions attributed to the State in 2016. Future research should (a) further validate the model with field experiments; (b) make a full life cycle assessment of the potential for greenhouse gas mitigation, including additional effects of biochar applications on greenhouse gas balances.
Project description:<h4>Background</h4>Food safety has become a major issue, with serious environmental pollution resulting from losses of nitrogen (N) fertilizers. N is a key element for plant growth and is often one of the most important yield-limiting nutrients in paddy soil. Urea-N immobilization is an important process for restoring the levels of soil nutrient depleted by rice production and sustaining productivity. The benefits of biochar application include improved soil fertility, altered N dynamics, and reduced nutrient leaching. However, due to high variability in the quality of biochar, the responses of N loss and rice productivity to biochar amendments, especially those prepared at different pyrolysis temperatures, are still unclear. The main objectives of the present study were to examine the effects of biochar prepared at different pyrolysis temperatures on fertilizer N immobilization in paddy soil and explore the underlying mechanisms.<h4>Methods</h4>Two biochar samples were prepared by pyrolysis of maize straw at 400 °C (B400) and 700 °C (B700), respectively. The biochar was applied to paddy soil at three rates (0, 0.7, and 2.1%, w/w), with or without N fertilization (0, 168, and 210 kg N ha<sup>-1</sup>). Pot experiments were performed to determine nitrous oxide (N<sub>2</sub>O) emissions and <sup>15</sup>N recovery from paddy soil using a <sup>15</sup>N tracer across the rice growing season.<h4>Results</h4>Compared with the non-biochar control, biochar significantly decreased soil bulk density while increasing soil porosity, irrespective of pyrolysis temperature and N fertilizer level. Under B400 and B700, a high biochar rate decreased N loss rate to 66.42 and 68.90%, whereas a high N level increased it to 77.21 and 76.99%, respectively. Biochar also markedly decreased N<sub>2</sub>O emissions to 1.06 (B400) and 0.75 kg ha<sup>-1</sup> (B700); low-N treatment caused a decrease in N<sub>2</sub>O emissions under B400, but this decrease was not observed under B700. An application rate of biochar of 2.1% plus 210 kg ha<sup>-1</sup> N fertilizer substantially decreased the N fertilizer-induced N<sub>2</sub>O emission factor under B400, whereas under B700 no significant difference was observed. Biochar combined with N fertilizer treatment decreased rice biomass and grain yield by an average of 51.55 and 23.90 g pot<sup>-1</sup>, respectively, but the yield reduction under B700 was lower than under B400.<h4>Conclusion</h4>Irrespective of pyrolysis temperature, biochar had a positive effect on residual soil <sup>15</sup>N content, while it negatively affected the <sup>15</sup>N recovery of rice, N<sub>2</sub>O emissions from soil, rice biomass, and grain yield in the first year. Generally, a high application rate of biochar prepared at high or low pyrolysis temperature reduced the N fertilizer-induced N<sub>2</sub>O emission factor considerably. These biochar effects were dependent on N fertilizer level, biochar application rate, and their interactions.
Project description:This study evaluates the benefits of mineral fertilizers replacement for biodigested vinasse. Data from experimental anaerobic digestion (AD) of vinasse were applied to support the analysis. Based on previous experiments, this assessment assumed that vinasse production could reach 2.38 × 10<sup>7</sup> m<sup>3</sup>/year generating around 66,585 MWh/year of electric energy from biogas burning in the Administrative Region of Campinas (ARC). This amount of energy could supply more than 103,000 inhabitants and avoid 35,892 tCO<sub>2eq</sub>/year (from electric energy replacement). The biodigested vinasse might also reduce the total N, P, and K mineral fertilizers demand per hectare of sugarcane crop in 30%, 1%, and 46%, respectively, avoiding additional greenhouse gas emissions of 111,877 tCO<sub>2</sub>eq/year. There is no biodigested vinasse surplus for a moderate fertigation rate of 100 m<sup>3</sup>/ha, complying with local environmental laws related to nutrients excess side effects in areas destined to sugarcane crop. Notwithstanding, a Geographic Information System analysis for a small adjacent area to ARC indicated nine different fertigation rates, ranging from 50 to 100 m<sup>3</sup>/ha. Even though the general analysis for ARC shows high NPK replacement levels, the fertigation practices should be subsidized for robust soil analysis and adequate to safe environmental levels. A management tool can be designed using the results here presented to subsidize investments for AD widespread adoption by the sugarcane industry to catch a reasonable practice from the economic and environmental perspectives.
Project description:<h4>Background</h4>Soil application of biochar and straw alone or their combinations with nitrogen (N) fertilizer are becoming increasingly common, but little is known about their agronomic and environmental performance in semiarid environments. This study was conducted to investigate the effect(s) of these amendments on soil properties, nitrous oxide (N<sub>2</sub>O) and methane (CH<sub>4</sub>) emissions and grain and biomass yield of spring wheat (<i>Triticum aestivum</i> L.), and to produce background dataset that may be used to inform nutrient management guidelines for semiarid environments.<h4>Methods</h4>The experiment involved the application of biochar, straw or urea (46% nitrogen [N]) alone or their combinations. The treatments were: CN<sub>0</sub>-control (zero-amendment), CN<sub>50</sub> -50 kg ha<sup>-1</sup> N, CN<sub>100</sub>-100 kg ha<sup>-1</sup> N, BN<sub>0</sub> -15 t ha<sup>-1</sup> biochar, BN<sub>50</sub>-15 t ha<sup>-1</sup> biochar + 50 kg ha<sup>-1</sup> N, BN<sub>100</sub>-15 t ha<sup>-1</sup> biochar + 100 kg ha<sup>-1</sup> N, SN<sub>0</sub> -4.5 t ha<sup>-1</sup> straw, SN<sub>50</sub> -4.5 t ha<sup>-1</sup> straw + 50 kg ha<sup>-1</sup> N and SN<sub>100</sub>-4.5 t ha<sup>-1</sup> straw + 100 kg ha<sup>-1</sup> N. Fluxes of N<sub>2</sub>O, CH<sub>4</sub> and grain yield were monitored over three consecutive cropping seasons between 2014 and 2016 using the static chamber-gas chromatography method.<h4>Results</h4>On average, BN<sub>100</sub>reported the highest grain yield (2054 kg ha<sup>-1</sup>), which was between 25.04% and 38.34% higher than all other treatments. In addition, biomass yield was much higher under biochar treated plots relative to the other treatments. These findings are supported by the increased in soil organic C by 17.14% and 21.65% in biochar amended soils (at 0-10 cm) compared to straw treated soils and soils without carbon respectively. The BN<sub>100</sub>treatment also improved bulk density and hydraulic properties (<i>P</i> < 0.05), which supported the above results. The greatest N<sub>2</sub>O emissions and CH<sub>4</sub> sink were recorded under the highest rate of N fertilization (100 kg N ha<sup>-1</sup>). Cumulative N<sub>2</sub>O emissions were 39.02% and 48.23% lower in BN<sub>100</sub> compared with CN<sub>0</sub> and CN<sub>100</sub>, respectively. There was also a ≈ 37.53% reduction in CH<sub>4</sub> uptake under BN<sub>100</sub>compared with CN<sub>0</sub>-control and CN<sub>50</sub>. The mean cumulative N<sub>2</sub>O emission from biochar treated soils had a significant decrease of 10.93% and 38.61% compared to straw treated soils and soils without carbon treatment, respectively. However, differences between mean cumulative N<sub>2</sub>O emission between straw treated soils and soils without carbon were not significant. These results indicate the dependency of crop yield, N<sub>2</sub>O and CH<sub>4</sub> emissions on soil quality and imply that crop productivity could be increased without compromising on environmental quality when biochar is applied in combination with N-fertilizer. The practice of applying biochar with N fertilizer at 100 kg ha<sup>-1</sup> N resulted in increases in crop productivity and reduced N<sub>2</sub>O and CH<sub>4</sub>soil emissions under dryland cropping systems.
Project description:Biochar has been shown to reduce soil emissions of CO2, CH4 and N2O in short-term incubation and greenhouse experiments. Such controlled experiments failed to represent variable field conditions, and rarely included crop growth feedback. The objective of this study was to assess the effect of biochar, in comparison to green manure and mineral nitrogen, on greenhouse gas Emissions Intensity (EI = emissions in CO2 equivalents per ton of grain yield) in a low-fertility tropical Ultisol. Using a field trial in western Kenya, biochar (0 and 2.5 t ha-1; made from Eucalyptus wood) was integrated with urea (0 and 120 kg N ha-1) and green manure (Tithonia diversifolia; 0, 2.5 and 5 t ha-1) in a factorial design for four consecutive seasons from October 2012 to August 2014. Compared to the control, biochar increased soil CO2 emissions (9-33%), reduced soil CH4 uptake (7-59%) and reduced soil N2O emissions (1-42%) in each season, with no seasonal differences. N2O emissions increased following amendment with T. diversifolia (6%) and urea (13%) compared to the control. Generally, N2O emissions decreased where only biochar was applied. The greatest decrease in N2O (42%) occurred where all three amendments were applied compared to when they were added separately. EI in response to any of the amendments was lower than the control, ranging from 9 to 65% (33.0 ± 3.2 = mean ± SE). The amendments increased SOC stocks by 0.1-1.2 t ha-1 year-1 (mean ± SE of 0.8 ± 0.09 t ha-1 year-1). The results suggest decreased net EI with biochar in low fertility soils mainly through greater net primary productivity (89% of the decrease).
Project description:<h4>Background</h4>Di-nitrogen oxide (N<sub>2</sub>O) emissions from soil may lead to nonpoint-source pollution in farmland. Improving the C and N content in the soil is an excellent strategy to reduce N<sub>2</sub>O emission and mitigate soil N loss. However, this method lacks a unified mathematical index or standard to evaluate its effect.<h4>Methods</h4>To quantify the impact of soil improvement (C and N) on N<sub>2</sub>O emissions, we conducted a 2-year field experiment using biochar as carbon source and fertilizer as nitrogen source, setting three treatments (fertilization (300 kg N ha<sup>-1</sup>), fertilization + biochar (30 t ha<sup>-1</sup>), control).<h4>Results</h4>Results indicate that after biochar application, the average soil water content above 20 cm increased by ∼26% and 26.92% in 2019, and ∼10% and 12.49% in 2020. The average soil temperature above 20 cm also increased by ∼2% and 3.41% in 2019. Fertigation significantly promotes the soil N2O emissions, and biochar application indeed inhibited the cumulation by approximately 52.4% in 2019 and 33.9% in 2020, respectively. N<sub>2</sub>O emissions strongly depend on the deep soil moisture and temperature (20-80 cm), in addition to the surface soil moisture and temperature (0-20 cm). Therefore, we established an exponential model between the soil moisture and N<sub>2</sub>O emissions based on theoretical analysis. We find that the N<sub>2</sub>O emissions exponentially increase with increasing soil moisture regardless of fertilization or biochar application. Furthermore, the coefficient a < 0 means that N<sub>2</sub>O emissions initially increase and then decrease. The a<sub>RU</sub> < a<sub>CK</sub> indicates that fertilization does promote the rate of N<sub>2</sub>O emissions, and the a<sub>BRU</sub> > a<sub>RU</sub> indicates that biochar application mitigates this rate induced by fertilization. This conclusion can be verified by the sensitivity coefficient (SC<sub>B</sub> of 1.02 and 14.74; SC<sub>U</sub> of 19.18 and 20.83). Thus, we believe the model can quantify the impact of soil C and N changes on N<sub>2</sub>O emissions. We can conclude that biochar does significantly reduce N<sub>2</sub>O emissions from farmland.
Project description:The efficacy of biochar as an environmentally friendly agent for non-point source and climate change mitigation remains uncertain. Our goal was to test the impact of biochar amendment on paddy rice nitrogen (N) uptake, soil N leaching, and soil CH<sub>4</sub> and N<sub>2</sub>O fluxes in northwest China. Biochar was applied at four rates (0, 4.5, 9 and13.5?t ha<sup>-1</sup> yr<sup>-1</sup>). Biochar amendment significantly increased rice N uptake, soil total N concentration and the abundance of soil ammonia-oxidizing archaea (AOA), but it significantly reduced the soil NO<sub>3</sub><sup>-</sup>-N concentration and soil bulk density. Biochar significantly reduced NO<sub>3</sub><sup>-</sup>-N and NH<sub>4</sub><sup>+</sup>-N leaching. The C2 and C3 treatments significantly increased the soil CH<sub>4</sub> flux and reduced the soil N<sub>2</sub>O flux, leading to significantly increased net global warming potential (GWP). Soil NO<sub>3</sub><sup>-</sup>-N rather than NH<sub>4</sub><sup>+</sup>-N was the key integrator of the soil CH<sub>4</sub> and N<sub>2</sub>O fluxes. Our results indicate that a shift in abundance of the AOA community and increased rice N uptake are closely linked to the reduced soil NO<sub>3</sub><sup>-</sup>-N concentration under biochar amendment. Furthermore, soil NO<sub>3</sub><sup>-</sup>-N availability plays an important role in regulating soil inorganic N leaching and net GWP in rice paddies in northwest China.
Project description:Silicon (Si) deficiency, caused by acidic soil and rainy climate, is a major constraint for sugarcane production in southern China. Si application generally improves sugarcane growth; however, there are few studies on the relationships between enhanced plant growth, changes in rhizosphere soil, and bacterial communities. A field experiment was conducted to measure sugarcane agronomic traits, plant nutrient contents, rhizosphere soil enzyme activities and chemical properties, and the rhizosphere bacterial community diversity and structure of three predominant sugarcane varieties under two Si treatments, i.e., 0 and 200 kg of silicon dioxide (SiO<sub>2</sub>) ha<sup>-1</sup> regarded as Si0 and Si200, respectively. Results showed that Si application substantially improved the sugarcane stalk fresh weight and Si, phosphorus (P), and potassium (K) contents comparing to Si0, and had an obvious impact on rhizosphere soil pH, available Si (ASi), available P (AP), available K (AK), total phosphorus (TP), and the activity of acid phosphatase. Furthermore, the relative abundances of <i>Proteobacteria</i> showed a remarkable increase in Si200, which may be the dominant group in sugarcane growth under Si application. Interestingly, the AP was noticed as a major factor that caused bacterial community structure differences between the two Si treatments according to canonical correspondence analysis (CCA). In addition, the association network analysis indicated that Si application enriched the rhizosphere bacterial network, which could be beneficial to sugarcane growth. Overall, appropriate Si application, i.e., 200 kg SiO<sub>2</sub> ha<sup>-1</sup> promoted sugarcane growth, changed rhizosphere soil enzyme activities and chemical properties, and bacterial community structures.
Project description:The sequestration in soil of organic carbon (SOC) derived from atmospheric carbon dioxide (CO<sub>2</sub>) by replacing arable crops with leys, has been measured over 70?years on a sandy loam soil. The experiment was designed initially to test the effect of leys on the yields of arable crops. A 3-year grazed grass with clover (grass?+?clover) ley in a 5-year rotation with arable crops increased percentage organic carbon (%OC) in the top 25?cm of the soil from 0.98 to 1.23 in 28?years, but with little further increase during the next 40?years with all-grass leys given fertilizer nitrogen (N). In this second period, OC inputs were balanced by losses, suggesting that about 1.3% OC might be near the equilibrium content for this rotation. Including 3-year lucerne (Medicago sativa) leys had little effect on %OC over 28?years, but after changing to grass?+?clover leys, %OC increased to 1.24 during the next 40?years. Eight-year leys (all grass with N or grass?+?clover) in 10-year rotations with arable crops were started in the 1970s, and after three rotations %OC had increased to ca. 1.40 in 2000-2009. Over 70?years, %OC declined from 0.98 to 0.94 in an all-arable rotation with mainly cereals and to 0.82 with more root crops. Applications of 38?t?ha<sup>-1</sup> farmyard manure (FYM) every fifth year increased %OC by 0.13% by the mid-1960s when applications ceased. Soil treated with FYM still contained 0.10% more OC in 2000-2009. Changes in the amount of OC have been modelled with RothC-26.3 and estimated inputs of C for selected rotations. Little of the OC input during the 70?years has been retained; most was retained in the grazed ley rotation, but 9?t?ha<sup>-1</sup> only of a total input of 189?t?ha<sup>-1</sup>. In other rotations more than 98% of the total OC input was lost. Despite large losses of C, annual increases in OC of 4‰ are possible on this soil type with the inclusion of grass or grass?+?clover leys or the application of FYM, but only for a limited period. Such increases in SOC might help to limit increases in atmospheric CO<sub>2</sub>.<h4>Highlights</h4>Can leys sequester significant amounts of atmospheric CO <sub>2</sub> in SOM and contribute to the 4‰ initiative?Changes in the percentage and amount of OC were measured and modelled over 70?years and OC losses estimated.Three-year grass or grass?+?clover leys increased %OC, but only to an equilibrium level that was then maintained.Despite large losses, sequestering CO <sub>2</sub>-C at 4‰?year<sup>-1</sup> by growing grass or grass?+?clover leys is possible.
Project description:As a result of metal mining activities in Pakistan, toxic heavy metals (HMs) such as chromium (Cr) and lead (Pb) often enter the soil ecosystem, accumulate in food crops and cause serious human health and environmental issues. Therefore, this study examined the efficacy of biochar for contaminated soil remediation. Poplar wood biochar (PWB) and sugarcane bagasse biochar (SCBB) were amended to mine-contaminated agricultural soil at 3% and 7% (wt/wt) application rates. Lactuca sativa (Lettuce) was cultivated in these soils in a greenhouse, and uptake of HMs (Cr and Pb) as well as biomass produced were measured. Subsequently, health risks were estimated from uptake data. When amended at 7%, both biochars significantly (P<0.01) reduced plant uptake of Cr and Pb in amended soil with significant (P<0.01) increase in biomass of lettuce as compared to the control. Risk assessment results showed that both biochars decreased the daily intake of metals (DIM) and associated health risk due to consumption of lettuce as compared to the control. The Pb human health risk index (HRI) for adults and children significantly (P<0.01) decreased with sugarcane bagasse biochar applied at 7% rate relative to other treatments (including the control). Relative to controls, the SCBB and PWB reduced Cr and Pb uptake in lettuce by 69%, 73.7%, respectively, and Pb by 57% and 47.4%, respectively. For both amendments, HRI values for Cr were within safe limits for adults and children. HRI values for Pb were not within safe limits except for the sugarcane bagasse biochar applied at 7%. Results of the study indicated that application of SCBB at 7% rate to mine impacted agricultural soil effectively increased plant biomass and reduced bioaccumulation, DIM and associated HRI of Cr and Pb as compared to other treatments and the control.
Project description:<h4>Background</h4>The greenhouse gas (GHG) mitigation is one of the most important environmental benefits of using bioenergy replacing fossil fuels. Nitrous oxide (N<sub>2</sub>O) and methane (CH<sub>4</sub>) are important GHGs and have drawn extra attention for their roles in global warming. Although there have been many works of soil emissions of N<sub>2</sub>O and CH<sub>4</sub> from bioenergy crops in the field scale, GHG emissions in large area of marginal lands are rather sparse and how soil temperature and moisture affect the emission potential remains unknown. Therefore, we sought to estimate the regional GHG emission based on N<sub>2</sub>O and CH<sub>4</sub> releases from the energy crop fields.<h4>Results</h4>Here we sampled the top soils from two <i>Miscanthus</i> fields and incubated them using a short-term laboratory microcosm approach under different conditions of typical soil temperatures and moistures. Based on the emission measurements of N<sub>2</sub>O and CH<sub>4</sub>, we developed a model to estimate annual regional GHG emission of <i>Miscanthus</i> production in the infertile Loess Plateau of China. The results showed that the N<sub>2</sub>O emission potential was 0.27 kg N ha<sup>-1</sup> year<sup>-1</sup> and clearly lower than that of croplands and grasslands. The CH<sub>4</sub> uptake potential was 1.06 kg C ha<sup>-1</sup> year<sup>-1</sup> and was slightly higher than that of croplands. Integrated with our previous study on the emission of CO<sub>2</sub>, the net greenhouse effect of three major GHGs (N<sub>2</sub>O, CH<sub>4</sub> and CO<sub>2</sub>) from <i>Miscanthus</i> fields was 4.08 t CO<sub>2eq</sub> ha<sup>-1</sup> year<sup>-1</sup> in the Loess Plateau, which was lower than that of croplands, grasslands and shrub lands.<h4>Conclusions</h4>Our study revealed that <i>Miscanthus</i> production may hold a great potential for GHG mitigation in the vast infertile land in the Loess Plateau of China and could contribute to the sustainable energy utilization and have positive environmental impact on the region.