Designer, acidic biochar influences calcareous soil characteristics

An acidic (pH 5.8) biochar was created using a low pyrolysis temperature (350 degrees celsius) and steam activation to potentially improve the soil physicochemical status of an eroded calcareous soil. Biochar was added at 0, 1, 2, and 10 percent (by weight) to an eroded Portneuf soil (coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcid) and destructively sampled at 1, 2, 3, 4, 5, and 6 month intervals. Soil was analyzed for volumetric water content, pH, nitrate-nitrogen, ammonium-nitrogen, plant-available iron, zinc, manganese, copper, and phosphorus, organic carbon, carbon dioxide respiration, and microbial enumeration via extractable DNA and 16S rRNA gene copies. Soil water content increased with biochar application regardless of rate; the response was consistent over time. Soil pH decreased between 0.2 and 0.4 units, while plant-available zinc, manganese, and phosphorus increased with increasing biochar application rate. Micronutrient availability tended to decrease over time likely due to the precipitation of insoluble mineral species. Increasing biochar application raised the soil organic carbon content and it remained elevated over time. Increasing biochar application rate also increased respired carbon dioxide, yet the carbon dioxide released decreased over time. Soil nitrate-nitrogen concentrations significantly decreased with increasing biochar application rate likely due to microbial immobilization. Depending on application rate, biochar produced a 1.4 to 2.1-fold increase in soil DNA extracted and 1.4- to 2.4-fold increase in 16S rRNA gene abundance over control soils, suggesting microbial stimulation and a subsequent burst of activity upon biochar addition. Our results showed that there is promise in designing a biochar to improve the quality of eroded calcareous soils with concomitant increases in soil microbial activity

Biochar elemental composition and factors influencing nutrient retention

Biochar is the carbonaceous solid byproduct of the thermochemical conversion of a carbon-bearing organic material, commonly high in cellulose, hemicelluloses, or lignin content, for the purposes of carbon sequestration and storage. More specifically, the thermal conversion process known as pyrolysis occurs when carbon-containing substances are introduced to elevated temperatures in the absence of oxygen at varying residence times, yielding biochar. Several pyrolysis techniques employed to produce biochar differ in the temperature of reaction and residence time in the reactor. Different reactor residence times are described as slow (hours to days), fast (seconds to minutes), and flash (seconds). Fast or flash pyrolysis typically occurs around 500oC with residence times less than 500 milliseconds to 1 second and produces relatively greater gas yields with a concomitant decrease in biochar yield (~ 12%). Slow pyrolysis temperatures have ranged from 350 to 750oC but with residence times ranging from minutes to days. Slow pyrolysis yields a greater quantity of biochar (between 25 to 35%). Pyrolysis temperature and type may be varied to maximize the desired biochar end-product. In general, increasing pyrolysis temperature tends to increase biochar total carbon, potassium, and magnesium content, pH, and surface area, and decrease cation exchange capacity. Slow pyrolysis, in general, tends to produce biochars with greater nitrogen, sulfur, available phosphorus, calcium, magnesium, surface area, and cation exchange capacity as compared to fast pyrolysis. In addition to altering temperature and time, the importance of feedstock source needs to be recognized when utilizing biochar in situations such as a soil conditioner. Over the last 10 years biochar research and use has expanded exponentially and so have the feedstocks utilized. Biochars have now been created from corn, wheat, barley and rice straw, switchgrass, peanut, pecan, and hazelnut shells, sugarcane bagasse, coconut coir, food waste, hardwood and softwood species, poultry and turkey litter, swine, dairy, and cattle manure, and biosolids to name a few. Feedstock source influences end-product characteristics, and in general most plant-based biochars containing elevated carbon content and lesser quantities of necessary plant nutrients as compared to manure-based biochars. It has been demonstrated that the mineral content of the feedstock has a significant effect on product distribution, with higher amounts of chloride salts reducing the amount of the solid biochar product. In addition, chloride and other inorganic salts also impact the chemical composition of the liquid, gas, and char pyrolysis products, potentially producing products with higher economic values. Existing studies indicate that even the trace amounts of minerals present in the various biomass sources and feedstock mixtures do have an impact on the chemical compositions of the products. Furthermore, both temperature and residence time, along with feedstock source or mixtures of sources, affect end-product characteristics

Addition of activated switchgrass biochar to an aridic subsoil increases microbial nitrogen cycling gene abundances

It has been demonstrated that soil amended with biochar, designed specifically for use as a soil conditioner, results in changes to the microbial populations that reside therein. These changes have been reflected in studies measuring variations in microbial activity, biomass, and community structure. Despite these studies, very few experiments have been performed examining microbial genes involved in nutrient cycling processes. Given the paucity of research in this area, we designed a six-month study in a Portneuf soil (coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcid) treated with three levels (1%, 2%, and 10% w/w ratio) of a biochar pyrolyzed from switchgrass (Panicum virgatum) at 350°C and steam activated at 800°C to measure the abundances of four genes involved in nitrogen (N) cycling. Gene abundances were measured using qPCR, with relative abundances of these genes calculated based on measurement of the 16S rDNA gene. At the end of the six-month study, all measured genes showed significantly greater abundances in biochar amended treatments as compared to the control, potentially increasing the amount of N cycled in soils receiving such treatments. In soil amended with 10% biochar, genes involved in nitrogen fixation (nifH), and denitrification (nirS), showed significantly increased relative abundances. Lastly, gene abundances and relative abundances correlated with soil characteristics, in particular nitrate nitrogen, % N and % carbon. In toto, these results confirm that activated switchgrass-derived biochar, designed for use as a soil conditioner, has an impact on the treated soils microbial communities. We therefore suggest that future use of biochar as a soil management practice should take into account not only changes to the soil's physiochemical properties, but its biological properties as well

Can forest management based on natural disturbances maintain ecological resilience?

Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance

Biochar elemental composition and factors influencing nutrient retention

Biochar is the carbonaceous solid byproduct of the thermochemical conversion of a carbon-bearing organic material, commonly high in cellulose, hemicelluloses, or lignin content, for the purposes of carbon sequestration and storage. More specifically, the thermal conversion process known as pyrolysis occurs when carbon-containing substances are introduced to elevated temperatures in the absence of oxygen at varying residence times, yielding biochar. Several pyrolysis techniques employed to produce biochar differ in the temperature of reaction and residence time in the reactor. Different reactor residence times are described as slow (hours to days), fast (seconds to minutes), and flash (seconds). Fast or flash pyrolysis typically occurs around 500oC with residence times less than 500 milliseconds to 1 second and produces relatively greater gas yields with a concomitant decrease in biochar yield (~ 12%). Slow pyrolysis temperatures have ranged from 350 to 750oC but with residence times ranging from minutes to days. Slow pyrolysis yields a greater quantity of biochar (between 25 to 35%). Pyrolysis temperature and type may be varied to maximize the desired biochar end-product. In general, increasing pyrolysis temperature tends to increase biochar total carbon, potassium, and magnesium content, pH, and surface area, and decrease cation exchange capacity. Slow pyrolysis, in general, tends to produce biochars with greater nitrogen, sulfur, available phosphorus, calcium, magnesium, surface area, and cation exchange capacity as compared to fast pyrolysis. In addition to altering temperature and time, the importance of feedstock source needs to be recognized when utilizing biochar in situations such as a soil conditioner. Over the last 10 years biochar research and use has expanded exponentially and so have the feedstocks utilized. Biochars have now been created from corn, wheat, barley and rice straw, switchgrass, peanut, pecan, and hazelnut shells, sugarcane bagasse, coconut coir, food waste, hardwood and softwood species, poultry and turkey litter, swine, dairy, and cattle manure, and biosolids to name a few. Feedstock source influences end-product characteristics, and in general most plant-based biochars containing elevated carbon content and lesser quantities of necessary plant nutrients as compared to manure-based biochars. It has been demonstrated that the mineral content of the feedstock has a significant effect on product distribution, with higher amounts of chloride salts reducing the amount of the solid biochar product. In addition, chloride and other inorganic salts also impact the chemical composition of the liquid, gas, and char pyrolysis products, potentially producing products with higher economic values. Existing studies indicate that even the trace amounts of minerals present in the various biomass sources and feedstock mixtures do have an impact on the chemical compositions of the products. Furthermore, both temperature and residence time, along with feedstock source or mixtures of sources, affect end-product characteristics