Comparing Biochar-Swine Manure Mixture to Conventional Manure Impact on Soil Nutrient Availability and Plant Uptake—A Greenhouse Study

The potential role of biochar in mitigating gaseous emissions from livestock waste - A mini-review

The livestock industry plays a significant role in the economic well-being of many parts of the world with a host of environmental challenges. Key amongst them is the management of gaseous emissions emitted from livestock manure. Mitigation of gaseous emissions from livestock operations such as odor, odorous volatile organic compounds (VOCs), ammonia (NH3), hydrogen sulfide (H2S), and greenhouse gases (GHGs) have been of research interest for the last couple of decades. Biochar, a low-cost-value byproduct of biorenewable energy and thermochemical waste processing compared with syngas and bio-oil, has been actively researched as a potential surficial treatment of manure and emissions from stored or co-composted manure. Yet, the efficacy of biochar treatment differs, partly because biochar properties vary with feedstock and thermochemical processing conditions. To date, the results from laboratory-scale trials are encouraging, but a more focused effort is needed to bring this technology closer to farm-scale applications. Therefore, this review aims to summarize and highlight current research related to mitigating gaseous emissions from manure treated with biochar. Various types of biochar, and modes of biochar applications, e.g., manure additives and co-composting, dosage, and timing, are discussed in the context of targeted gas emissions mitigation. Gaps in knowledge remain, including demonstrated larger-scale mitigation performance and verifiable technoecomics. Standardization and certification of biochar properties suitable for specific environmental management applications are recommended. The potential synergy between mitigating emissions, improving manure quality, carbon, and nitrogen cycling in animal and crop production agriculture is found. Biochar can be a comprehensive solution to gaseous emissions while also upgrading manure as a high-quality additive that could improve the sustainability of animal and crop production systems.

The impact of the application of compochar on soil moisture, stress, yield and nutritional properties of legumes under drought stress

Nowadays, when climate change is becoming more and more evident, drought stress plays a very important role, including in agriculture. The increasing number of years with extreme temperatures in the Czech Republic has a negative impact on agricultural production, among other things. Therefore, ways are being sought to reduce these negative impacts. One of them may be the use of compochar (a mixture of compost and biochar) to improve water retention in the soil. The effect of compochar addition on soil properties and crop yield was tested under conditions simulating severe drought stress (greenhouse experiments) compared to normal conditions (field experiments). The aim was to find the most suitable ratio of compochar addition that would reduce the negative effects of drought stress on the yield and quality of peas and beans. Tested soil was only able to retain water between 0.03 and 0.18 cm3/cm3, while the compochar itself retained between 0.12 and 0.32 cm3 cm-3. Three substrate variants were tested by varying the amount of compochar (10, 30 and 50 % v/v) in the soil, and all three substrates showed a similar water content between 0.03 and 0.21 cm3 cm-3 depending on the planted crop and week of cultivation. No apparent stress was observed in crops planted in 100 % compochar. Nevertheless, in general, the trend of chlorophyll a/b ratio increased with increasing amounts of compochar in the soil, indicating stress. Yield increased by approximately 50 % for both test crops when 30 % compochar was used as substrate. The flavonoid content in beans was between 410 and 500 μg CE g-1 DW and in peas was approximately 300 μg CE g-1 DW. The results showed that the utilization of compochar had no effect on either total phenol content, flavonoid content or antioxidant capacity. The combination of compochar with soil (30 %) was found to positively affect the (i) soil moisture, (ii) crop yield, and (iii) nutritional properties of peas and beans and (iv) the ability of plants to withstand drought stress.

Co-application of biochar and compost with decreased N fertilizer reduced annual ammonia emissions in wetland rice

Ammonia (NH3) emission from rice fields is a dominant nitrogen (N) loss pathway causing negative impacts on farm profitability and the environment. Reducing N fertilizer application to compensate for N inputs in organic amendments was evaluated for effects on N loss via volatilization, rice yields and post-harvest soil properties in an annual irrigated rice (Boro) – pre-monsoon rice (Aus) – monsoon (Aman) rice sequence. That experiment was conducted using the integrated plant nutrition system (IPNS; nutrient contents in organic amendments were subtracted from the full recommended fertilizer dose i.e., RD of chemical fertilizers) where six treatments with four replications were applied in each season: (T1) no fertilizer (control), (T2) RD, (T3) poultry manure biochar (3 t ha−1; pyrolyzed at 450°C) + decreased dose of recommended fertilizer (DRD), (T4) rice husk ash (3 t ha−1) + DRD, (T5) compost (3 t ha−1) + DRD, and (T6) compost (1.5 t ha−1)+ biochar (1.5 t ha−1) + DRD. The N loss via volatilization varied twofold among seasons being 16% in irrigated rice and 29% in the pre-monsoon rice crop. In irrigated rice, T6 had significantly lower NH3 emissions than all other treatments, except the control while in pre-monsoon and monsoon seasons, T6 and T3 were alike. Pooling the three seasons together, biochar (T3) or biochar plus compost (T6) reduced NH3 loss via volatilization by 36-37% while compost alone (T5) reduced NH3 loss by 23% relative to RD. Biochar (T3) and biochar plus compost mixture (T6) reduced yield-scaled NH3 emissions by 40 and 47% relative to the RD of chemical fertilizer (T2). The organic amendments with IPNS reduced the quantity of N fertilizer application by 65, 7, 24, and 45% in T3, T4, T5, and T6 treatments, respectively, while rice yields and soil chemical properties in all seasons were similar to the RD. This study suggests that incorporation of biochar alone or co-applied with compost and decrease of N fertilizer on an IPNS basis in rice-based cropping systems can reduce N application rates and NH3 emissions without harming yield or soil quality.

Biochar in manure can suppress water stress of sugar beet (Beta vulgaris) and increase sucrose content in tubers

Increased soil drought events threaten the yields of sugar beet (Beta vulgaris L.) and other staples of arable production in central Europe. In this study we evaluated soil moisture and nutrients as impacted by a two and five % (wt) addition of biochar, manure and their blend to a loamy-sand Regosol. Cyclical soil drought was achieved by the controlled reduction of watering by 75% in pot experiments. Ongoing soil moisture and nutrient measurements were taken, and physiological parameters of sugar beet plants were analysed three weeks after the induced drought. At the end of the experiment (16 weeks) plants were harvested and their mass assessed, as well as their nutrient, pigment and sugar contents. In contrast to the addition of manure, soil volumetric water contents were two to three times greater after biochar amendment, compared to the control soil. Porewater analysis revealed that nutrient leaching (e.g., NO₃^-, K⁺) from manure addition to soil was reduced when biochar was blended in (by ≤86% compared to manure alone). Crop analysis showed that leaf gas exchanges were moderated during drought following soil amendment, and leaf and tuber yields were increased furthest when combined biochar-manure blends were applied (> 2-times compared to the control). Perhaps most importantly, the advantageous soil conditions induced by the combined biochar and manure addition also resulted in significantly increased sugar contents in plants (2.4-times) pointing to immediate practical applications of these results in the field.

Dataset Documenting the Interactions of Biochar with Manure, Soil, and Plants: Towards Improved Sustainability of Animal and Crop Agriculture

Plant and animal agriculture is a part of a larger system where the environment, soil, water, and nutrient management interact. Biochar (a pyrolyzed biomass) has been shown to affect the single components of this complex system positively. Biochar is a soil amendment, which has been documented for its benefits as a soil enhancer particularly to increase soil carbon, improve soil fertility, and better nutrient retention. These effects have been documented in the literature. Still, there is a need for a broader examination of these single components and effects that aims at the complementarity and synergy attainable with biochar and the animal and crop-production system. Thus, we report a comprehensive dataset documenting the interactions of biochar with manure, soil, and plants. We evaluated three biochars mixed with manure alongside both manure and soil controls for improvement in soil quality, reduction in nutrient movement, and increase in plant nutrient availability. We explain the experiments and the dataset that contains the physicochemical properties of each biochar–manure mixture, the physicochemical properties of soil amended with each biochar–manure mixture, and the biomass and nutrient information of plants grown in biochar–manure mixture-amended soil. This dataset is useful for continued research examining both the short- and long-term effects of biochar–manure mixtures on both plant and soil systems. In addition, these data will be beneficial to extend the findings to field settings for practical and realized gains.

Integrated Fertilizers Synergistically Bolster Temperate Soybean Growth, Yield, and Oil Content

For ensuring food security and imparting sustainability to modern commercial-oriented and highly intensive temperate farming systems, organic wastes from poultry and dairy industries constitute biologically viable strategy to improve crops productivity under changing climate. A field trial was undertaken to appraise the impact of broiler litter (BL = 5 tons ha−1), farm yard slurry (FYS = 10 tons ha−1), and chemical fertilizers including di-ammonium phosphate (DAP = 60 kg ha−1) and single super phosphate (SSP = 60 kg ha−1) applied solely and in conjunction with each other, along with a control treatment (NM). The synergistic fertilization regime encompassing BL+DAP triggered the vegetative growth of soybean as indicated by taller plants having thicker stems and higher leaf area per plant compared to NM. In addition, this fertilization management system improved reproductive yield attributes including pods number and 100-seeds weight which maximized the seed yield, harvest index, seed oil content, and biological yield by 66%, 5%, 31%, and 23% respectively than NM. Moreover, this fertilizers combination was followed by SSP + BL, while BL performed better than FYS and DAP remained superior to SSP. Furthermore, the correlation analyses indicated moderately stronger direct association of seed yield with vegetative growth traits and highly stronger linear relationship with reproductive yield attributes. Thus, co-application of broiler litter (5 tons ha−1) with reduced doses of DAP (60 kg ha−1) might be recommended to temperate soybean growers having access to poultry wastes.

Mitigation of Acute Hydrogen Sulfide and Ammonia Emissions from Swine Manure during Three-Hour Agitation Using Pelletized Biochar

The risk of inhalation exposure to elevated concentrations of hydrogen sulfide (H2S) and ammonia (NH3) during the agitation of stored swine manure is high. Once or twice a year, farmers agitate manure before pump-out and application to fields. Agitation of the swine manure causes the short-term releases of highly toxic levels of H2S and NH3. In our previous pilot-scale studies, the biochar powder showed significant mitigation of H2S and NH3 emissions when it was surficially applied to manure immediately before agitation. However, fine biochar powder application poses hazards by itself and may not be practical to apply on a farm scale, especially when livestock and workers are present. We hypothesized that applying pelletized biochar to manure surfaces is just as effective as applying powder to protect farmers and animals from excessive exposure to H2S and NH3. This work reports on the lab-scale proof-of-the-concept trials with biochar pellets on the lab scale. The objective was to compare the biochar pellets and biochar powder on their effectiveness of mitigation on H2S and NH3 gases during 3-h-long swine manure agitation. Three scenarios were compared in (n = 3) trials: (i) control, (ii) 12.5 mm thick surficial application to manure surface of biochar powder, and (iii) an equivalent (by mass) dose of pelletized biochar applied to the manure surface. The biochar powder was bound with 35% (wt) water into ~5 × 10 mm (dia × length) pellets. The biochar powder was significantly (p < 0.05) more effective than the biochar pellets. Still, pellets reduced total H2S and NH3 emissions by ~72% and ~68%, respectively (p = 0.001), compared with ~99% by powder (p = 0.001). The maximum H2S and NH3 concentrations were reduced from 48.1 ± 4.8 ppm and 1810 ± 850 ppm to 20.8 ± 2.95 ppm and 775 ± 182 ppm by pellets, and to 22.1 ± 16.9 ppm and 40.3 ± 57 ppm by powder, respectively. These reductions are equivalent to reducing the maximum concentrations of H2S and NH3 during the 3-h manure agitation by 57% and 57% (pellets) and 54% and 98% (powder), respectively. Treated manure properties hinted at improved nitrogen retention, yet they were not significant due to high variability. We recommend scaling up and trials on the farm-scale level using biochar pellets to assess the feasibility of application to large manure surfaces and techno-economic evaluation.