Nils Borchard

Biochar Affected by Composting with Farmyard Manure

Biochar applications to soils can improve soil fertility by increasing the soils cation exchange capacity (CEC) and nutrient retention. Because biochar amendment may occur with the applications of organic fertilizers, we tested to which extent composting with farmyard manure increases CEC and nutrient content of charcoal and gasification coke. Both types of biochar absorbed leachate generated during the composting process. As a result, the moisture content of gasification coke increased from 0.02 to 0.94 g g, and that of charcoal increased from 0.03 to 0.52 g g. With the leachate, the chars absorbed organic matter and nutrients, increasing contents of water-extractable organic carbon (gasification coke: from 0.09 to 7.00 g kg; charcoal: from 0.03 to 3.52 g kg), total soluble nitrogen (gasification coke: from not detected to 705.5 mg kg; charcoal: from 3.2 to 377.2 mg kg), plant-available phosphorus (gasification coke: from 351 to 635 mg kg; charcoal: from 44 to 190 mg kg), and plant-available potassium (gasification coke: from 6.0 to 15.3 g kg; charcoal: from 0.6 to 8.5 g kg). The potential CEC increased from 22.4 to 88.6 mmol kg for the gasification coke and from 20.8 to 39.0 mmol kg for the charcoal. There were little if any changes in the contents and patterns of benzene polycarboxylic acids of the biochars, suggesting that degradation of black carbon during the composting process was negligible. The surface area of the biochars declined during the composting process due to the clogging of micropores by sorbed compost-derived materials. Interactions with composting substrate thus enhance the nutrient loads but alter the surface properties of biochars.

Greenhouse gas production in mixtures of soil with composted and noncomposted biochars is governed by char-associated organic compounds.

Biochar application to soil has the potential to increase soil productivity while reducing anthropogenic greenhouse gas (GHG) emissions to the atmosphere. However, techniques for conditioning this material for maximizing its effects as a soil amendment require elucidation. We examined changes of organic matter associated with two biochars after 175 d of composting and the resulting effects on GHG emissions during a 150-d incubation period. Composting decreased the amount of organic compounds that could be thermally released from the biochars and affected their molecular nature. These thermally desorbable organic compounds from initial biochars likely stimulated the oxidation of CH and inhibited the production of NO in soil-biochar mixtures. However, these reductions of GHG emissions disappeared together with thermally desorbable organic compounds after the composting of chars. Instead, addition of composted gasification coke and charcoal stimulated the formation of CH and increased NO emissions by 45 to 56%. Nitrous oxide emissions equaled 20% of the total amount of N added with composted biochars, suggesting that organic compounds and N sorbed by the chars during composting fueled GHG production. The transient nature of the suppression of CH and NO production challenges the long-term GHG mitigation potential of biochar in soil.

Biochar-Mediated [14C]Atrazine Mineralization in Atrazine-Adapted Soils from Belgium and Brazil

Biochar addition to soil has been reported to reduce the microbial degradation of pesticides due to sorption of the active compound. This study investigated whether the addition of hardwood biochar alters the mineralization of (14)C-labeled atrazine in two atrazine-adapted soils from Belgium and Brazil at different moisture regimens. Biochar addition resulted in an equally high or even in a significantly higher atrazine mineralization compared to the soils without biochar. Statistical analysis revealed that the extent of atrazine mineralization was more influenced by the specific soil than by the addition of biochar. It was concluded that biochar amendment up to 5% by weight does not negatively affect the mineralization of atrazine by an atrazine-adapted soil microflora.

Biochar as a tool to reduce the agricultural greenhouse-gas burden – knowns, unknowns and future research needs

Agriculture and land use change has significantly increased atmospheric emissions of the non-CO2 green-house gases (GHG) nitrous oxide (N2O) and methane (CH4). Since human nutritional and bioenergy needs continue to increase, at a shrinking global land area for production, novel land management strategies are required that reduce the GHG footprint per unit of yield. Here we review the potential of biochar to reduce N2O and CH4 emissions from agricultural practices including potential mechanisms behind observed effects. Furthermore, we investigate alternative uses of biochar in agricultural land management that may significantly reduce the GHG-emissions-per-unit-of-product footprint, such as (i) pyrolysis of manures as hygienic alternative to direct soil application, (ii) using biochar as fertilizer carrier matrix for underfoot fertilization, biochar use (iii) as composting additive or (iv) as feed additive in animal husbandry or for manure treatment. We conclude that the largest future research needs lay in conducting life-cycle GHG assessments when using biochar as an on-farm management tool for nutrient-rich biomass waste streams.

A Three-Dimensional View on Soil Biogeochemistry: A Dataset for a Forested Headwater Catchment

Current understanding of the variability in soil properties and their relationship to processes and spatial patterns in forested landscapes is limited due to the scarcity of datasets providing such information. Here we present a spatially highly resolved dataset () that provides detailed information on the three-dimensional variability of biogeochemical properties in the Wüstebach catchment (western Germany), a long-term environmental observation site of the TERENO (Terrestrial Environmental Observatories) project. High-resolution soil sampling was conducted, and physical and biogeochemical soil parameters were recorded per horizon. The dataset is helpful in the analysis of the spatial heterogeneity in biogeochemical properties within soil horizons and with depth through the soil profile. In addition, it shows links between hydrological and biogeochemical properties and processes within the system. Overall, the dataset provides a high-resolution view into (re)cycling, leaching, and storage of nutrients on the catchment scale in a forested headwater catchment.

Carbon accrual rates, vegetation and nutrient dynamics in a regularly burned coppice woodland in Germany

Historically, large areas of forest in Europe were managed as coppice woodland to produce wood‐based fuel for the smelting industry. We hypothesized that this practice produced a legacy effect on current forest ecosystem properties. Specifically, we hypothesized that the historical form of coppicing may have produced a legacy of elevated stocks of soil organic carbon (SOC), nutrients and black carbon (BC) in soil as fire was routinely used in coppiced woodland to clear land. We further hypothesized that these changes in soil properties would result in increased biodiversity. To test these hypotheses, we sampled the surface soil (0–5, 5–10 and 10–20 cm) from a chronosequence of forest sites found in the Siegerland (Germany) that had been coppiced and burned 1, 2, 3.5, 6, 8, 11 and 17 years before present. Mature beech and spruce forests (i.e., >60 years) were also sampled as reference sites: to provide a hint of what might occur in the absence of human intervention. We measured stocks of SOC, BC, NO3‐N, P, K, Mg, as well as cation exchange and water‐holding capacity, and we mapped plant composition to calculate species richness and evenness. The results showed that coppicing in combination with burning soil and litter improved soil nutrient availability, enhanced biodiversity and increased SOC stocks. The SOC stocks and biodiversity were increased by a factor of three relative to those in the mature beech and spruce forests. This study shows that traditional coppicing practice may facilitate net C accrual rates of 20 t ha−1 yr−1 and maintain high biodiversity, indicating that aspects of traditional practice could be applied in current forest management to foster biodiversity and to mitigate climate change.

New Tropical Peatland Gas and Particulate Emissions Factors Indicate 2015 Indonesian Fires Released Far More Particulate Matter (but Less Methane) than Current Inventories Imply

Deforestation and draining of the peatlands in equatorial SE Asia has greatly increased their flammability, and in September–October 2015 a strong El Nino-related drought led to further drying and to widespread burning across parts of Indonesia, primarily on Kalimantan and Sumatra. These fires resulted in some of the worst sustained outdoor air pollution ever recorded, with atmospheric particulate matter (PM) concentrations exceeding those considered “extremely hazardous to health” by up to an order of magnitude. Here we report unique in situ air quality data and tropical peatland fire emissions factors (EFs) for key carbonaceous trace gases (CO2, CH4 and CO) and PM2.5 and black carbon (BC) particulates, based on measurements conducted on Kalimantan at the height of the 2015 fires, both at locations of “pure” sub-surface peat burning and spreading vegetation fires atop burning peat. PM2.5 are the most significant smoke constituent in terms of human health impacts, and we find in situ PM2.5 emissions factors for pure peat burning to be 17.8 to 22.3 g·kg−1, and for spreading vegetation fires atop burning peat 44 to 61 g·kg−1, both far higher than past laboratory burning of tropical peat has suggested. The latter are some of the highest PM2.5 emissions factors measured worldwide. Using our peatland CO2, CH4 and CO emissions factors (1779 ± 55 g·kg−1, 238 ± 36 g·kg−1, and 7.8 ± 2.3 g·kg−1 respectively) alongside in situ measured peat carbon content (610 ± 47 g-C·kg−1) we provide a new 358 Tg (± 30%) fuel consumption estimate for the 2015 Indonesian fires, which is less than that provided by the GFEDv4.1s and GFASv1.2 global fire emissions inventories by 23% and 34% respectively, and which due to our lower EFCH4 produces far less (~3×) methane. However, our mean in situ derived EFPM2.5 for these extreme tropical peatland fires (28 ± 6 g·kg−1) is far higher than current emissions inventories assume, resulting in our total PM2.5 emissions estimate (9.1 ± 3.5 Tg) being many times higher than GFEDv4.1s, GFASv1.2 and FINNv2, despite our lower fuel consumption. We find that two thirds of the emitted PM2.5 come from Kalimantan, one third from Sumatra, and 95% from burning peatlands. Using new geostationary fire radiative power (FRP) data we map the fire emissions’ spatio-temporal variations in far greater detail than ever before (hourly, 0.05°), identifying a tropical peatland fire diurnal cycle twice as wide as in neighboring non-peat areas and peaking much later in the day. Our data show that a combination of greatly elevated PM2.5 emissions factors, large areas of simultaneous, long-duration burning, and very high peat fuel consumption per unit area made these Sept to Oct tropical peatland fires the greatest wildfire source of particulate matter globally in 2015, furthering evidence for a regional atmospheric pollution impact whose particulate matter component in particular led to millions of citizens being exposed to extremely poor levels of air quality for substantial periods.

Biochar, soil and land-use interactions that reduce nitrate leaching and N2O emissions: A meta-analysis

Biochar can reduce both nitrous oxide (N2O) emissions and nitrate (NO3-) leaching, but refining biochars use for estimating these types of losses remains elusive. For example, biochar properties such as ash content and labile organic compounds may induce transient effects that alter N-based losses. Thus, the aim of this meta-analysis was to assess interactions between biochar-induced effects on N2O emissions and NO3- retention, regarding the duration of experiments as well as soil and land use properties. Data were compiled from 88 peer-reviewed publications resulting in 608 observations up to May 2016 and corresponding response ratios were used to perform a random effects meta-analysis, testing biochars impact on cumulative N2O emissions, soil NO3- concentrations and leaching in temperate, semi-arid, sub-tropical, and tropical climate. The overall N2O emissions reduction was 38%, but N2O emission reductions tended to be negligible after one year. Overall, soil NO3- concentrations remained unaffected while NO3- leaching was reduced by 13% with biochar; greater leaching reductions (>26%) occurred over longer experimental times (i.e. >30 days). Biochar had the strongest N2O-emission reducing effect in paddy soils (Anthrosols) and sandy soils (Arenosols). The use of biochar reduced both N2O emissions and NO3- leaching in arable farming and horticulture, but it did not affect these losses in grasslands and perennial crops. In conclusion, the time-dependent impact on N2O emissions and NO3- leaching is a crucial factor that needs to be considered in order to develop and test resilient and sustainable biochar-based N loss mitigation strategies. Our results provide a valuable starting point for future biochar-based N loss mitigation studies.