Resource utilization conditions as biochar of an invasive plant Spartina alterniflora in coastal wetlands of China

Converting feedstocks of invasive plants into biochar is a new and cost‐effective measure for their control, and benefits for the sustainable development of native ecosystems. Spartina alterniflora, an invasive plant widely distributed in coastal wetlands of China, was used to produce biochar. We aimed to analyze how S. alterniflora biochar properties changed with desalination of feedstocks, pyrolysis temperature, and residence time. Results showed that desalting feedstocks increased biochar pH, stability, porosity, and surface area, but diminished biochar yield and polarity. Pyrolysis temperature positively affected biochar pH, surface area, and pore volume, while it had negative effects on biochar yield, oxygen and hydrogen contents, hydrogen/carbon and oxygen/carbon ratios, pore size, and function groups. However, residence time of pyrolysis had slight effects on biochar properties. The results are valuable for optimizing pyrolysis temperature and pretreatment measure of feedstocks, to tune S. alterniflora biochar properties for specific environmental usage.     

Phytolith‐rich biochar: A potential Si fertilizer in desilicated soils

Silicon (Si) is beneficial to plants since it increases photosynthetic efficiency, and alleviates biotic and abiotic stresses. In the most highly weathered and desilicated soils, plant phytoliths make up the reservoir of bioavailable Si. The regular removal of crop residues, however, substantially decreases this pool. Si supply may therefore be required to sustain continuous cropping. Available Si fertilizers are costly and usually poor in soluble Si. Biochar produced from the pyrolysis of phytolith‐rich biomass is thus a promising alternative Si source for plants. Taking into account the challenges of increasing food demand and environmental concerns, we evaluate the global potential of biochar produced from major crop residues and manures in terms of phytogenic Si (PhSi) supply. Crop residues contribute to 80% of the global production of biomass dry matter (8,201 Tg/year) of which 3,137 Tg/year are potentially available after pyrolysis, giving a potential application rate of 1.7 T ha^?1 year^?1 for highly weathered soils in the tropics. The potential PhSi supply from crop biochar amounts to 102 Tg Si/year. On its own, rice straws produce 57.7 Tg PhSi/year, accounting for 56.6% of the potential annual PhSi production. The Si release from crop biochar depends on inter altere feedstock type, pyrolysis temperature, soil pH, and buffer capacity. Furthermore, the amplitude of plant Si uptake and mineralomass depends on plant species, soil properties, and processes. These factors interact and can exert a decisive influence on the effectiveness of phytolithic biochar in releasing Si into highly weathered soils. We conclude that the use of phytolithic biochar as a Si fertilizer offers undeniable potential to mitigate desilication and to enhance Si ecological services due to soil weathering and biomass removal. This potential must be explored, as well as the conditions for using biochar in the field.     

施用生物炭6年后对稻田土壤酶活性及肥力的影响

利用田间定位试验,研究0(BC₀)、7.5(BC₁)、15(BC₂)和22.5(BC₃)t·hm^-2水稻秸秆生物炭及3.75 t·hm^-2水稻秸秆(STR)一次性施加6年后对稻田土壤肥力及酶活性的影响.结果表明: 施用生物炭6年后土壤有机碳、有效磷和速效钾含量显著增加,增幅分别为34.6%、12.4%和26.2%,土壤pH值和容重显著降低,但对土壤全氮含量无显著影响.土壤脲酶和酸性磷酸酶的活性显著增加,土壤荧光素二乙酸酯酶(FDA水解酶)和芳基硫酸酯酶的活性受到不同程度的抑制,其中,BC₂处理的土壤脲酶活性增加量最大,增幅为36.5%.土壤酸性磷酸酶活性随着生物炭施加量的增加而增加,与土壤速效磷含量呈显著正相关关系;土壤FDA水解酶和脲酶主要与土壤速效钾含量有关;酸性磷酸酶和芳基硫酸酯酶与土壤容重呈显著正相关.施用生物炭6年后土壤脱氢酶和多酚氧化酶活性明显升高,增幅分别为48.8%和27.5%,而过氧化氢酶活性逐渐下降,且显著低于对照BC₀.STR处理显著增加了土壤脲酶、FDA水解酶、脱氢酶、酸性磷酸酶和芳基硫酸酯酶的活性,降低了过氧化氢酶和多酚氧化酶的活性,降幅分别为23.4%和15.9%.     

Legal constraints and opportunities for biochar: a case analysis of EU law

This article addresses biochar from a legal point of view. It analyses different policies and regulations from a European (Flemish) point of view and provides a first and general insight in what potential legal constraints the development of a biochar industry might face and what opportunities lie ahead. This is due to the fact that biochar is a recent product and a lot of scientific uncertainty still exists regarding the consequences of its application. From the analysis it appears a multitude of policies and legislative measures influence the development of the biochar industry. Hence, it is important that all these policies and legislative measures are analyzed in an appropriate manner. Moreover, considerable lobbying, negotiating and cooperation between different disciplines (legal, scientific, economical, etc.) will be required so as to develop a feasible and safe biochar framework.     

A meta-analysis on pyrogenic organic matter induced priming effect

Pyrogenic organic matter (PyOM) is considered an important soil carbon (C) sink. However, there are evidences that its addition to soil may induce a priming effect (PE) thus influencing its C abatement potential. The direction, the size and the mechanisms responsible for PyOM induced PE are far from being understood. We collected approximately 650 data points from 18 studies to analyse the characteristics of the PE induced by PyOM. The database was divided between the PE induced on the native soil organic matter and on fresh organic matter. Most of the studies were short-term incubation therefore the projections of findings on the long term may be critical. Our findings indicate that over 1 year PyOM induces an average positive PE of 0.3 mg C g⁻¹ soil on native soil organic matter and a PE of approximately the same size but opposite direction on fresh organic matter. We studied the correlation of PE with several properties of soil, of the added PyOM, and time after PyOM addition. We found that PyOM primes positively the native soil organic matter in the first 20 days while negative PE appears in a later stage. Negative PE was correlated with the soil C content. PyOM characterized by a low C content induced a higher positive PE on native soil organic carbon. No correlation was found between the factors record in our database and the PE induced on the fresh organic matter. We reviewed the mechanisms proposed in literature to explain PE and discussed them based on findings from our meta-analysis. We believe that the presence of a labile fraction in PyOM may trigger the activity of soil microorganisms on the short term and therefore induce a positive PE, while on the long term PyOM may induce a negative PE by promoting physical protection mechanisms.     

Competing uses for China's straw: the economic and carbon abatement potential of biochar

China is under pressure to improve its agricultural productivity to keep up with the demands of a growing population with increasingly resource‐intensive diets. This productivity improvement must occur against a backdrop of carbon intensity reduction targets, and a highly fragmented, nutrient‐inefficient farming system. Moreover, the Chinese government increasingly recognizes the need to rationalize the management of the 800 million tonnes of agricultural crop straw that China produces each year, up to 40% of which is burned in‐field as a waste. Biochar produced from these residues and applied to land could contribute to China's agricultural productivity, resource use efficiency and carbon reduction goals. However competing uses for China's straw residues are rapidly emerging, particularly from bioenergy generation. Therefore it is important to understand the relative economic viability and carbon abatement potential of directing agricultural residues to biochar rather than bioenergy. Using cost‐benefit analysis (CBA) and life‐cycle analysis (LCA), this paper therefore compares the economic viability and carbon abatement potential of biochar production via pyrolysis, with that of bioenergy production via briquetting and gasification. Straw reincorporation and in‐field straw burning are used as baseline scenarios. We find that briquetting straw for heat energy is the most cost‐effective carbon abatement technology, requiring a subsidy of $7 MgCO₂e^?1 abated. However China's current bioelectricity subsidy scheme makes gasification (NPV $12.6 million) more financially attractive for investors than both briquetting (NPV $7.34 million), and pyrolysis ($?1.84 million). The direct carbon abatement potential of pyrolysis (1.06 MgCO₂e per odt straw) is also lower than that of briquetting (1.35 MgCO₂e per odt straw) and gasification (1.16 MgCO₂e per odt straw). However indirect carbon abatement processes arising from biochar application could significantly improve the carbon abatement potential of the pyrolysis scenario. Likewise, increasing the agronomic value of biochar is essential for the pyrolysis scenario to compete as an economically viable, cost‐effective mitigation technology.     

Removal of Chromium (VI) from Aqueous Solution Using Mycelial Pellets of Penicillium simplicissimum Impregnated with Powdered Biochar

The mycelia pellets of Penicillium simplicissimum impregnated with powdered biochar (MPPSIPB) were synthesized and applied to remove chromium (VI) from aqueous solution. The effects of pH, MPPSIPB dosage, initial Cr(VI) concentration, and contact time were investigated via batch experiments. Results indicated that the percentage removal of Cr(VI) was significantly dependent on the pH of the solution. Ten grams mycelial pellets and 0.2 g powdered biochar could form the most stable pellets. The maximum value of biosorption of Cr(VI) was 28.0 mg/g. Scanning electron microscopy (SEM) analysis showed that the mycelia pellets of Penicillium simplicissimum had abundant filamentous network, which entrapped powdered biochar firmly. Fourier transform infrared (FTIR) analysis suggested that O?H, N?H, C?H, C?O, and C?OH groups from MPPSIPB were involved in chromium binding and the subsequent reduction. Kinetic studies indicated that the pseudo-second-order equation fit best for Cr(VI) removal from aqueous solution. Freundlich isotherm was found to apply better for the adsorption equilibrium data with respect to the Langmuir isotherm. Furthermore, MPPSIPB can be separated from aqueous solution completely by filtration. Both experimental study and modeling results indicated that MPPSIPB exhibited remarkable affinity for chromate and had a potential application in Cr(VI) removal from water.     

Biochar amendment to soils impairs developmental and reproductive performances of a major rice pest Nilaparvata lugens (Homopera: Delphacidae)

Biochar amendments to soils had aroused much interest for having potential for greenhouse gas mitigation, soil improvement and increased crop productivity. However, little attention had been focused on the influence of biochar amendments on herbivorous insect pests. This study investigated whether a biochar amendment affected developmental and reproductive performances of the rice brown planthopper (Nilaparvata lugens) feeding on rice plants. The biochar from the pyrolysis of wheat straw was used for treatments of soils (from a fallow rice field), and the treated soils were applied to grow rice seedlings in small vials, in which N. lugens life history was observed. The nymphal development time was delayed and nymph‐to‐adult survival decreased with a high level of 200 g/kg biochar application. Herbivore lifetime fecundity decreased with increasing amounts of biochar, from 256 eggs under the control down to 69 eggs under the high level (200 g/kg) of biochar application. Egg‐hatching rate significantly decreased at the highest biochar level (200 g/kg), compared to the other lower biochar levels. Our results suggest that biochar amendment to rice fields may have negative impacts on the rice brown planthoppers when applied at level of 200 g/kg of soil.