The need for organic soil amendments is increasing in the Republic of Korea against the backdrop of increased soil acidification and nutrient losses. The pyrolysis of biomass produces biochar which not only increases soil productivity but also provides environmental benefits through carbon sequestration. The portion of the brewer’s spent grain (BSG) recycled is by far less than the amount generated, but pyrolysis can help to reverse this trend by turning BSG waste into a valuable soil amendment. The current study, therefore, evaluated the effects of brewer’s spent grain biochar (BB_XXX) produced at three different temperatures of 300 °C, 500 °C and 700 °C on the yield and quality characteristics of the leaf lettuce as well as the effects on soil chemical properties through a pot experiment. Each of the BB_XXX and BSG were added to the soil at two rates of 2% and 5% by weight. The pH and carbon content of the BBxxx increased with increasing pyrolysis temperatures and the trend was replicated in the soil upon biochar application i.e. the soil pH and carbon content increased alongside temperatures at which biochar was pyrolyzed. On the other hand, however, the soil electrical conductivity (EC) diminished with the increasing pyrolysis temperatures of the biochar applied. With regards to crop growth, the BB₅₀₀ 5% amendment produced the highest marketable yield of the leaf lettuce and while the lettuce grown on the control produced leaf lettuce with the lowest content of nitrate nitrogen, BB₅₀₀ 5% amendment generally produced the highest quality lettuce. The results indicate that BB₅₀₀ performed agronomically better than the rest of the amendments and is thus recommended as an effective BSG recycling measure.

NH₃ emitted into the atmosphere undergoes intricate chemical reactions to form fine particulate matter PM_2.5. Nitrogen fertilizers are one of the major sources of gaseous ammonia. Recently, research into using biochar to lessen NH₃ emissions from agricultural land has taken center stage and several studies have been executed in that regard. However, biochar’s capacity to reduce emissions of gaseous NH₃ from applied nitrogen fertilizers is affected by both soil and biochar properties. While the effects of soil properties on NH₃ volatilizations have been widely studied, the data concerning the effects of biochar properties on NH₃ volatilizations from the soil are still scanty. It is against this backdrop that this study examined the effects of biochar pH on emissions of NH₃ from the soil amended with varying quantities of nitrogen, as well as the impact on the growth and productivity of Chinese cabbage. To achieve the study objectives, acidic (pH 5.7), neutral (pH 6.7) and alkaline (pH 11.0) biochars were used and each was added to the soil at a rate of 1% (w/w). Nitrogen fertilizers were applied at three rates of 160, 320, 640 kg ha⁻¹. In comparison with the control, the acidic, neutral and alkaline biochar amendments reduced NH₃ emissions by up to 18%, 20% and 15%, respectively. However, only neutral biochar produced higher Chinese cabbage yields than the urea-only amendment and the Chinese cabbage yields increased with the increasing rates of nitrogen applied. Combined applications of neutral biochar and 640 kg/ha of nitrogen are recommended for optimal cabbage yields and low NH₃ emissions.

There is a paucity of data regarding the effect of nutrient-enriched biochar amendments on nutrient dynamics in both soil and crops. This is important because unlike pristine biochar, nutrient-enriched biochar is applied to the soil in minute quantities as large amounts may led to over application of the nutrients loaded in it. The current study examined the effects of both phosphorus- and nitrogen-enriched biochars on the dynamics of both macro and micronutrients in the sandy soil and leaf lettuce grown thereon. The phosphorus enrichment followed co-pyrolysis of animal manure (cow dung) with 25% and 50% bone meal (w/w), while the nitrogen enrichment was achieved by soaking the co-pyrolyzed biochar into urea and urea-hydrogen peroxide. The performances of the nutrient-enriched biochar were compared with the conventional amendment of urea and triple superphosphate (TSP) in the production of leaf lettuce over a period of two seasons in a pot experiment. The nutrient-enriched biochar amendments resulted into higher microbial biomass carbon and carbon to nitrogen ratios than the conventional amendment. The conventional amendment caused more phosphorus, potassium, and magnesium accumulations in the leaf lettuce than the nutrient-enriched biochar amendments. The nutrient-enriched biochar amendments led to more accumulations of nitrogen, calcium, and micronutrient elements in the leaf lettuce and availabilities of all the nutrient elements in the soil and thus, nutrient-enriched biochar acted as a reservoir that could provide nutrients to the growing lettuce beyond a single growing season.

This study explores the potential application of rice husk biochars, categorized by their pH (acidic, pH 5.98; neutral, pH 7.02; and alkali, pH 11.21) and particle sizes (micron-scale and sub-centimeter) in aquatic ecosystems for efficient removal of ammonium (NH₄⁺). To assess the NH₄⁺ adsorption capacity of the rice husk biochars, both NH₄⁺ adsorption kinetics and isotherms were employed. Additionally, we propose future prospects for utilizing rice husk biochar as an efficient adsorbent based on a review of previous studies. Our findings suggest that the NH₄⁺adsorption capacity of rice husk biochars is primarily influenced by their surface characteristics, specifically surface area of rice husk biochars and loss of acidic functional groups. In this study, the neutral rice husk biochars, which had the highest surface area at 9.86 m² g⁻¹, exhibited the highest NH₄⁺adsorption performance at 1.12 mg g⁻¹ (micron-scale) and 0.94 mg g⁻¹ (sub-centimeter) compared to acidic and alkali rice husk biochars. Additionally, particle size control proves to be a promising strategy for enhancing adsorption efficiency of rice husk biochars, with the micron-scale rice husk biochars being 1.19-fold higher than sub-centimeter ones. However, before implementing biochar-based pollutant removal strategies in aquatic ecosystems, several considerations (e.g., the potential harmfulness of inner components in biochar, side effects of biochar on aquatic life, and tracking the fate of biochar in aquatic ecosystems) must be addressed. By addressing these concerns, we can expect to expand the practical application of biochar for remediation in aquatic environments, contributing to the effective management of pollutants.

Current organic fertilizers are manufactured from imported ingredients, leading to unstable nutrient supply and high price fluctuations. These issues act as factors that hinder the use organic fertilizers, so in order to promote sustainable agriculture, it is necessary to domestically produce ingredients. In this study, the feasibility of substituting imported ingredients was evaluated by blending biochar derived from spent coffee grounds (SCGs) into organic fertilizers and applying it to kale-grown soils. To manufacture the SCGs biochar-based organic fertilizers, SCGs were pyrolyzed at 600℃ for 0.5 h, and the resulting biochar was mixed with soybean-meal and rice bran. Additionally, the SCGs biochar-based organic fertilizers were categorized based on the ratio of the SCGs biochar content (20-50%). The content of the SCGs biochar in organic fertilizer showed a positive correlation with the soil chemical properties, including soil pH, carbon, and organic matter content. However, the available nitrogen and potassium contents did not vary with the SCGs biochar content in organic fertilizer. This indicates that the SCGs biochar does not supply nutrients to the soil directly, while improving the soil chemical properties. Nonetheless, the kale yield was highest with the organic fertilizer containing 50% of the SCGs biochar at 5.18 Mg•ha-1 , which was 1.42-fold higher than the kale yield in untreated soil. Thus, increasing the content of the SCGs biochar in organic fertilizer effectively enahced kale yield by improving soil chemical properties. These findings suggest that the biochar could potentially substitute the imported ingredients in organic fertilizer, which often lead to price volatility and inconsistent quality.