Spruce Biochar Research Articles

Comparative Experimental Assessment of Pollutant Emission Behavior in Combustion of Untreated and Thermally Treated Solid Biofuels from Spruce Chips and Rapeseed Straw

Biomass energy for heating is going to be part of the spectrum of renewable energy sources. However, biomass combustion produces emissions of various pollutants with negative effects at both local and global scales. To reduce some of the locally important pollutant load, thermally treated biomass fuels may offer a partial solution. In this study, two biomass feedstocks, i.e., spruce chips and rapeseed straw, were thermally treated at 300 °C to produce biochars. Subsequently, both original materials and biochars were burned in a 25 kW retort combustion device. In both cases, the biochar showed lower emissions of carbon monoxide and nitrogen oxides, usually almost across the whole range of tested combustion conditions. In total, for the emission production per unit of net calorific value, the spruce biochar showed reductions in CO and NOx productions of 10.8% and 14.5%, respectively. More importantly, in rapeseed straw biochar, the difference was more pronounced. The total production was reduced by 28% and 42%, again in CO and NOx emissions, respectively.

Adsorption of common greywater pollutants and nutrients by various biochars as potential amendments for nature-based systems: Laboratory tests and molecular dynamics

Spruce wood and Typha (wetland plant) derived biochars pyrolyzed at 350 °C and 600 °C were tested for their sorption affinity for organic pollutants (diclofenac, methylparaben, benzotriazole and sodium 1-decanesulfonate) and nutrients (nitrate, ammonium, phosphate and boron) commonly found in greywater. Batch and column studies combined with molecular dynamics modelling determined the sorption capacity, kinetics, and described the underlying mechanisms. The spruce biochar (600 °C) exhibited the highest sorption capacity mainly for the tested organics. The dynamic test performed for spruce biochar (600 °C) showed that the magnitude of desorption was low, and the desorbed amount ranged between 3 and 11 %. Molecular dynamics modelling (a computational tool for elucidating molecular-level interactions) indicated that the increased sorption of nitrate and boron on spruce biochar (600 °C) could be attributed to hydrophobic interactions. The molecular dynamics shows that predominant adsorption of organic pollutants was governed by π-π stacking, with a minor role of hydrogen-bonding on the biochar surface. In summary, higher pyrolysis temperature biochar yielded greater adsorption capacity greywater borne contaminants and the reaction temperature (10–34 °C) and presence of anionic surfactant had a limited effect on the adsorption of organic pollutants, suggesting efficacious application of biochar in general for greywater treatment in nature-based systems.

Treatment of fish processing plant wastewater using dissolved air flotation and pilot-scale biochar column filtration

Wastewaters from fish processing cause a high organic load for municipal wastewater treatment and can interfere with treatment operations due to their high oil and grease content. In the present study, a modular dissolved air flotation (DAF) unit was used to remove oil, grease and other suspended solids from fish processing plant wastewater. After DAF treatment, the residual particles and nutrients were adsorbed onto a mixture of hemp and spruce biochar in a pilot-scale column filtration system. The proposed integrated treatment process aims to improve the quality of the fish processing wastewater, facilitate water reuse, and recover the dissolved nutrients in a reusable form. The DAF treatment removed nearly all the oil and grease from the wastewater. Also, chemical oxygen demand, turbidity and phosphorus concentration clearly decreased during the DAF process. The biochar filtration further clarified the DAF-treated wastewater and partly adsorbed the residual nutrients. Furthermore, in the spent biochar mixture, the nitrogen and phosphorus content increased significantly (N to 9.1–10.5 mg/g, P to 0.32–1.38 mg/g), which indicates the improved properties of the biochar as a possible soil conditioner.

Effects of biochar and ligneous soil amendments on greenhouse gas exchange during extremely dry growing season in a Finnish cropland

Organic soil amendments such as manure, biochar and compost are among the most efficient and widely used methods to increase soil carbon sequestration in agricultural soils. Even though their benefits are well known, many wood-derived materials are not yet utilized in Nordic agriculture due to a lack of incentives and knowledge of their effects in the local climate. We studied greenhouse gas exchange, plant growth and soil properties of a clay soil cultivated with oat in southern Finland in an extremely dry year. Two years earlier, the field was treated with three ligneous soil amendments—lime-stabilized fiber from the pulp industry, willow biochar and spruce biochar—which we compared against fertilized and non-fertilized controls. We found that the soil amendments increased porosity and the mean soil water holding capacity, which was most noticeable in plots amended with spruce biochar. There was a trend indicating that the mean yield and overall biomass production were larger in plots with soil amendments; however, the difference to unamended control was seldom significant due to the high variance among replicates. Manual chamber measurements revealed that carbon dioxide and methane exchange rates were reduced most probably by the exceptionally hot and dry weather conditions, but no differences could be found between the amended and unamended treatments. The nitrous oxide emissions were significantly smaller from the vegetated soil amended with willow biochar compared with the unamended control. Emissions from non-vegetated soil, representing heterotrophic respiration, were similar but without significant differences between treatments. Overall, the studied soil amendments indicated positive climatic impact two years after their application, but further research is needed to conclusively characterize the specific effects of organic soil amendments on processes affecting greenhouse gas exchange and plant growth.

Potential of Biochar to Reduce Greenhouse Gas Emissions and Increase Nitrogen Use Efficiency in Boreal Arable Soils in the Long-Term

Biochars have potential to provide agricultural and environmental benefits such as increasing soil carbon sequestration, crop yield, and soil fertility while reducing greenhouse gas (GHG) emissions and nitrogen leaching. However, whether these effects will sustain for the long-term is still unknown. Moreover, these effects were observed mostly in highly weathered (sub-) tropical soils with low pH and soil organic carbon (SOC). The soils in northern colder boreal regions have typically higher SOC and undergo continuous freeze-thaw cycles. Therefore, effects of biochars in these regions may be different from those observed in other climates. However, only a few biochar studies have been conducted in boreal regions. We aimed to assess the long-term effects of biochars on GHG emissions, yield-normalized non-CO2 GHG emissions (GHGI), and N dynamics in boreal soils. For this, we collected data from four existing Finnish biochar field experiments during 2018 growing season. The experiments were Jokioinen (Stagnosol), Qvidja (Cambisol), Viikki-1 (Stagnosol), and Viikki-2 (Umbrisol), where biochars were applied, 2, 2, 8, and 7 years before, respectively. The GHG emissions, crop yield, soil mineral N, and microbial biomass were measured from all fields, whereas, additional measurements of plant N contents and N leaching were conducted in Qvidja. Biochars increased CO2 efflux in Qvidja and Viikki-2, whereas, there were no statistically significant effects of biochars on the fluxes of N2O or CH4, but in Qvidja, biochars tended to reduce N2O fluxes at the peak emission points. The tendency of biochars to reduce N2O emissions seemed higher in soils with higher silt content and lower initial soil carbon. We demonstrated the long-term effects of biochar on increased crop yield by 65% and reduced GHGI by 43% in Viikki-2. In Qvidja, the significant increment of plant biomass, plant N uptake, nitrogen use efficiency, and crop yield, and reduction of NO3−–N leaching by the spruce biochar is attributed to its ability to retain NO3−–N, which could be linked to its significantly higher specific surface area. The ability of the spruce biochar to retain soil NO3−–N and hence to reduce N losses, has implications for sustainable management of N fertilization.

Biochar Capacity to Mitigate Acidity and Adsorb Metals—Laboratory Tests for Acid Sulfate Soil Drainage Water

A 96-h laboratory experiment was conducted to assess the potential of biochar as a water protection tool for acid sulfate soil runoff. Acid sulfate soils pose a risk to water bodies due to acid, metal-rich runoff, especially in drained peatland forests. New water protection methods, such as adsorption with biochar, are needed. We investigated the capability of spruce and birch biochar to adsorb metals and reduce acidity in the water. Water from an acid sulfate site was stirred with biochar, biochar with lime, and biochar with ash. We determined water Al, S, Fe, Cu, Co, Cd, Ni, and Zn concentrations periodically, as well as pH and total organic carbon at the beginning and the end of the experiment. The studied substances are considered the most abundant and environmentally harmful elements in the acid sulfate soils in Finland. Biochar surface characteristics were analyzed with FTIR spectroscopy. Concentration changes were used to parametrize adsorption kinetics models. Biochar adsorbed metals and increased pH, but lime and ash additives did not always improve the adsorption. Spruce biochar and ash addition had generally higher adsorption than birch biochar and lime addition. The adsorption was dominated by Al and Fe at lower pH, while increasing pH improved the adsorption of Cd and Zn. The results show that biochar can increase the water pH, as well as adsorb Al, Fe, Co, Cd, Ni, and Zn. Further work could include an actual-scale biochar reactor in a laboratory and field conditions.

Nitrogen Recovery from Clear-Cut Forest Runoff Using Biochar: Adsorption\u2013Desorption Dynamics Affected by Water Nitrogen Concentration

Forest regeneration operations increase the concentration of nitrogen (N) in watercourses especially outside the growing season when traditional biological water protection methods are inefficient. Biochar adsorption-based water treatment could be a solution for nutrient retention. We studied the total nitrogen (TN) and nitrate–nitrogen (NO3−–N) adsorption–desorption properties of spruce and birch biochar. The adsorption test was performed under four different initial concentrations of TN (1, 2, 3, and 4 mg L−1) using forest runoff water collected from ditch drains of boreal harvested peatland. The results showed that the TN adsorption amount increased linearly from the lowest to the highest concentration. The maximum adsorption capacity was 2.4 and 3.2 times greater in the highest concentration (4 mg L−1) compared to the lowest concentration (1 mg L−1) in spruce and birch biochar, respectively. The NO3−–N adsorption amount of birch biochar increased linearly from 0 to 0.15 mg NO3−–N g biochar−1 when the initial concentration of NO3−–N increased from 0.2 to 1.4 mg L−1. However, in spruce biochar, the initial concentration did not affect NO3−–N adsorption amount. The results indicate that concentration significantly affects the biochar’s capacity to adsorb N from water. The desorption test was performed by adding biochar extracted from the adsorption test into the forest runoff water with low TN concentration (0.2 or 0.35 mg L−1). The desorption results showed that desorption was negligibly small, and it was dependent on the TN concentration for birch biochar. Therefore, biochar can be a complementary method supporting water purification in peatland areas.

Potential of biochar soil amendments to reduce N leaching in boreal field conditions estimated using the resin bag method

Addition of biochar to soil has been shown to reduce nitrogen (N) leaching in pot experiments, but direct field measurements are scarce, and data is lacking especially from colder, boreal conditions. We studied the effect of soil organic amendments on nitrate (NO3-) and ammonium (NH4+) leaching using the resin bag method, by placing the bags containing ion-exchange resins under the plough layer. We compared N leaching under five different treatments at the Päästösäästö project site (Soilfood Oy) in Parainen, south-western Finland: non-fertilized control, fertilized control, and three different organic amendments: spruce biochar, willow biochar and nutrient fiber. During the 2017 growing season, resin bags were changed monthly between the end of May and beginning of September, extracted with 1 M NaCl, and analyzed for inorganic N. The daily leaching rate of NO3- was greatest at the beginning of the growing season, right after fertilization. Ammonium leaching was generally lower, and independent of the time since fertilization. The spruce biochar reduced cumulative NO3- leaching by 68% compared to the fertilized control. The NH4+ leaching in the organic amendment treatments did not statistically significantly differ from the fertilized control in pairwise comparisons. In October 2017, after harvesting, the resin bags were placed under soil columns again, and left in the soil over winter to accumulate N leached during the plant-free period. Cumulative NO3- leaching during winter was consistent with the corresponding summer results, and average leaching decreased in the order: willow biochar > fertilized control > nutrient fiber > non-fertilized control > spruce biochar. Thus, we show here, for the first time in a field study from boreal conditions that spruce biochar soil application decreased nitrate leaching, while increasing its retention in the surface layer of the biochar-amended soil.

Long-term effects of biochar application on greenhouse gas production and microbial community in temperate forest soils under increasing temperature

Biochar management has been proposed as a promising strategy to mitigate climate change. However, the long-term effects of biochar amendment on soil greenhouse gas (GHG) production and microbial community in forest ecosystems under projected warming remain highly uncertain. In this study, we conducted a 49-day incubation experiment to investigate the impact of biochar application on soil physico-chemical properties, GHG production rates, and microbial community at three temperature levels using a temperate forest soil amended with spruce biochar four years ago. Our results showed that temperature exerted a positive effect on soil CO2, CH4 and N2O production, leading to an increase in total global warming potential by 169% and 87% as temperature rose from 5 to 15 °C and from 15 to 25 °C, respectively, and thus a positive feedback to warming. Moreover, warming was found to reduce soil microbial biomass significantly, but at the same time promote the selection of an activated microbial community towards some phyla, e.g. Acidobacteria and Actinobacteria. We observed that biochar amendment reduced soil CH4 consumption and N2O production in the absence of litter by 106% and 94%, respectively, but did not affect soil CO2 production. While biochar had no significant influence of total global warming potential of forest soil, it could promote climate change mitigation by increasing the total soil carbon content by 26% in the presence of litter. In addition, biochar application was shown to enhance soil available phosphorus and dissolved organic carbon concentrations, as well as soil microbial biomass under a warmer environment. Our findings highlighted the potential of spruce biochar as a soil amendment in improving soil fertility and carbon sequestration in temperate forest over the long term, without creating any adverse climatic impacts associated with soil GHG production.

Simultaneous adsorption and biodegradation of trichloroethylene occurs in a biochar packed column treating contaminated landfill leachate

Trichloroethylene (TCE) is a human carcinogen that is commonly found in landfill leachate. Contaminated leachate plumes may be intercepted prior to reaching groundwater and treated in situ using permeable reactive barriers (PRB). This study used a packed column system containing herbal pomace and spruce biochar, previously shown to have TCE adsorptive capabilities. Influent containing raw or autoclaved landfill leachate was used to investigate the potential for environmental micro-organisms to establish a TCE-dechlorinating biofilm on the biochar, in order to prolong the operational life span of the system. TCE removal ≥ 99.7 % was observed by both biochars. No dichloroethylene (DCE) isomers were present in the column effluents, but cis-1,2 DCE was adsorbed to the biochar treating raw landfill leachate, indicating that dechlorination was occurring biologically in these columns. Known microbial species that are individually capable of complete dechlorination of TCE to ethene were not detected by 16S rRNA gene sequencing, but several species capable of partial TCE dechlorination (Desulfitobacterium spp., Sulfurospirillium spp. and Desulfuromonas spp) were present in the biofilms of the columns treating raw landfill leachate. These data demonstrate that biochar from waste material may be capable of supporting a dechlorinating biofilm to promote bioremediation of TCE.

Short-term effects of biochar on soil CO2 efflux in boreal Scots pine forests

Key messageDuring the first summer, wood biochar amendments increased soil temperature, pH, and soil CO2effluxes in a xeric boreal Scots pine forest. The increase of soil CO2efflux could be largely explained by increases in by soil temperature. Higher biochar application rates (1.0 vs 0.5 kg m−2) led to higher soil CO2efflux while the pyrolysis temperature of biochar (500 or 650 °C) had no effect on soil CO2efflux.ContextUsing biochar as a soil amendment has been proposed to increase the carbon sequestration in soils. However, a more rapid soil organic matter turnover after biochar application might reduce the effectiveness of biochar applications for carbon sequestration. By raising the pyrolysis temperature, biochar with lower contents of labile carbohydrates can be produced.AimsTo better understand the effects of biochar on boreal forest soil, we applied two spruce biochar with different pyrolysis temperatures (500 °C and 650 °C) at amounts of 1.0 and 0.5 kg m−2 in a young xeric Scots pine forest in southern Finland.MethodsSoil CO2, microbial biomass, and physiochemical properties were measured to track changes after biochar application during the first summer.ResultsSoil CO2 increased 14.3% in 1.0 kg m−2 treatments and 4.6% in 0.5 kg m−2. Soil temperature and pH were obviously higher in the 1.0 kg m−2 treatments. Differences in soil CO2 among treatments disappear after correcting by soil temperature and soil moisture.ConclusionBiochar increased soil CO2 mainly by raising soil temperature in the short term. Higher biochar application rates led to higher soil CO2 effluxes. The increase in soil CO2 efflux may be transient. More studies are needed to get the optimum biochar amount for carbon sequestration in boreal forest.

Biochar as adsorbent in purification of clear-cut forest runoff water: adsorption rate and adsorption capacity

Forest management practices in boreal peatlands increase nutrient export and suspended solids to watercourses calling for development of new water protection methods. One potential solution could be adsorption-based purification of runoff water using biochar. The aim of this study was to determine the adsorption rate and capacity for Norway spruce and silver birch biochars to design a biochar-filled reactor for a ditch drain. In a 10-day laboratory experiment, biochar was stirred with runoff water from a clear-cut peatland forest, and changes in water pH, total nitrogen, nitrate nitrogen, ammonium nitrogen, phosphorus, and total organic carbon concentrations were measured. Based on the concentration changes, adsorption was quantified and adsorption model containing the adsorption rate and capacity was fitted to the data. Our results indicate that biochar effectively adsorbs both inorganic and organic nitrogen from runoff water. Birch biochar had higher adsorption capacity of nitrogen than spruce biochar. This study demonstrates that the adsorption of nitrogen compounds onto biochar surfaces increases with increasing initial concentrations. Thus, aquatic ecosystems exposed to high nutrient loads from fertile peatlands would particularly benefit from biochar-based water purification.

Pyrolysed waste materials show potential for remediation of trichloroethylene-contaminated water

Trichloroethylene (TCE) is an Environmental Protection Agency priority pollutant associated with cancer in humans. With numerous industrial applications and regular landfill disposal, TCE is a common landfill leachate pollutant. In situ treatment barriers use costly fill materials such as granular activated carbon (GAC). Here, we show that while a range of untreated waste materials had little ability to adsorb TCE, waste-derived biochar showed excellent capacity for TCE adsorption. TCE removal efficiencies by spruce and oak-derived biochars were > 99.5 %, outperforming GAC (95 %) and herbal pomace biochar (93 %). A contact time of at least 32 h was required to reach equilibrium for all of these media. Assessment of pollution swapping potential revealed release of phosphate by all biochars. Analysis of media surface characteristics by Fourier Transform Infrared Spectroscopy (FTIR) predicted that GAC should have the highest ability to adsorb TCE, followed by Oak Biochar, Herbal Pomace Biochar 1, and Spruce Biochar 2, which was not in agreement with the experimental adsorption data. These data demonstrate the potential for pyrolysed waste material to be used as an alternative fill material for in situ remediation applications, thereby also addressing the European Circular Economy Strategy.

A study of densified biochar as carbon source in the silicon and ferrosilicon production

Biochar pellets were investigated as renewable reducing agents in substitution of coal and coke in the silicon and ferrosilicon production, where a high reactivity, good mechanical properties and low feedstock costs are appreciated. The usage of pyrolysis oil as binder was investigated as way to improve the quality of the pellets. Norway spruce biochar produced at 500, 800 and 1100 °C, was pelletized blended with pyrolysis oil and lignosulphonate. A second heat treatment was carried out at the same temperatures to evaluate the interaction between biochar and pyrolysis oil and to imitate the thermal stability of the pellets when used in a furnace. Density, tensile strength and mechanical durability were analyzed before and after the second heat treatment. The CO2 reactivity was investigated under non-steady conditions. It was observed that the pellet quality is affected by the pyrolysis temperature, showing a relevant difference in properties between 500 °C and 800 °C. The combination of lignosulphonate and pyrolysis oil improved considerably the density and mechanical durability of the pellets. By the second heat treatment, the quality of the pellets was bettered significantly. Densification seems to reduce CO2 reactivity; however, pellets showed a still high reactivity.

Immobilizing Laccase on Different Species Wood Biochar to Remove the Chlorinated Biphenyl in Wastewater

Biochars produced from two different wood species over a microwave assisted pyrolysis process were used as novel and green-based supports for immobilizing enzyme, laccase in particular. The results obtained from FT-IR, SEM and BET measurements indicated that Maple biochar with honeycomb structure has higher surface area and pore volume than Spruce biochar; and there exist O-H, C-H, C=O and C=C groups in biochars for potential chemical modification. The best laccase immobilization conditions identified from an orthogonal experiment were pH = 3, laccase concentration 16 g/L and contact time 8 h. Under such conditions, the high immobilization yield (64.2%) and amount (11.14 mg/g) of laccase on Maple biochar were achieved, leading to the significantly improved thermal stability of laccase. Moreover, the immobilized laccase is reusable and enhanced the enzymatic degradation of 4-hydroxy-3,5-dichlorobiphenyl (71.4% yield), thus creating a promising and novel type of adsorbent in the removal of polychlorinated biphenyls from wastewater.

Biochar addition changed the nutrient content and runoff water quality from the top layer of a grass field during simulated snowmelt

Biochar has the potential to decrease the leaching of nutrients from agricultural systems to watercourses. We applied cattle slurry (0 or 40 t ha−1) and different amounts of spruce biochar (0, 10, 20 or 40 t ha−1) to the surface of a boreal grass field in autumn and analyzed the nutrient content in the soil and the regrowth of grass (Phleum pratense) in the autumn over three years. In addition, four grass mats from each treatment were lifted each autumn and stored for 2–3 months outdoors (between −36 °C and 12 °C) for simulated snowmelt experiments. In the following winter, 30 kg snow was added to the grass mats and slowly melted with infra-red heaters over a 7-day period. All surface runoff water was collected and the concentrations of nitrate nitrogen (NO3-N), ammonium nitrogen (NH4-N), total nitrogen (TN), dissolved phosphate phosphorus (PO4-P), total phosphorus (TP), dissolved total potassium (K), dissolved organic carbon (DOC) and pH were measured. Biochar temporarily improved growing conditions by increasing pH values and the content of plant available acid ammonium acetate extractable P (PAc) and K (KAc) in the soil, which also increased losses in surface runoff during the first snowmelt. In contrast, the biochar retained slurry- and mineral fertilizer-originated NO3-N on the soil during the three year experiment and prevented NO3-N losses in surface runoff during the first snowmelt after autumnal slurry addition. The biochar-induced increase in phosphorus (P) loss in surface runoff during the first snowmelt after slurry application was considerable (0.1–0.5 kg P ha−1) and the decrease in nitrogen (N) loss was moderate (0.2–0.6 kg N ha−1) compared to annual P and N losses in surface runoff in an adjacent field. The surface application of biochar can be recommended for the inhibition of nutrient losses to watercourses via surface runoff only if the capacity of used biochar to retain both N and P can be verified before application.

Magnetite-coated biochar as a soil phosphate filter: From laboratory to field lysimeter

Agriculture is one of the largest anthropogenic contributors of phosphorus (P) to surface waters and reducing these P loads is a target set by many countries. One potential mitigation strategy could be to utilize biochar, functionalized by co-precipitating metal ions onto its surface to adsorb phosphates. We evaluated such an approach in a series of laboratory experiments and a three-year field lysimeter study. Leached phosphates were trapped in a 3-cm layer of a commercially available 20% hardwood/80% Norway spruce biochar, coated with magnetite and placed under the soil root zone. Langmuir maximum adsorption potential (Qmax) was 3.38 mg P g−1 biochar, as determined from batch adsorption studies performed at pH 6.5. Further laboratory experiments revealed that adsorption was strongly negatively correlated with pH (R2 = 0.995). In a laboratory column study using high flow rates, no difference was found in phosphate adsorption between coated biochar and the control (no biochar), after application of ammonium phosphate at a rate corresponding to 22 kg P ha−1. However, differences were observed at higher application rates (285 or 570 kg P ha−1). Calculation of a Fe:P molar ratio to evaluate the magnetite treatment method from laboratory (2:1) to lysimeter (248:1) suggested a relatively effective laboratory performance, but overall poor field efficiency. Nevertheless, biochar in the lysimeter study still reduced phosphate leaching from two organic soils, by 62% (P < 0.05) and 35% (NS). This suggests that, even though the method of magnetite-coating biochar is not necessarily resource-efficient, it is effective in removing P from soil leachate.

Biosorption (removing) of Cd(II), Cu(II) and methylene blue using biochar produced by different pyrolysis conditions of beech and spruce sawdust

The influence of pyrolysis parameters (temperature, heating rate) on adsorption properties of wood charcoals was studied. Beech and spruce waste sawdust were investigated by TG–MS technique, and it was revealed that pyrolysis of sawdust consists at least of two overlapping reactions characterized by different values of activation energy E a (151 and 184 kJ/mol for beech sawdust, 157 and 172 kJ/mol for spruce sawdust). Based on obtained results, adsorbents from studied sawdust were prepared through pyrolysis at 400–700 °C with heating rate 10 or 2 K/min and their surface and adsorption characteristics were investigated. It was found that higher pyrolysis temperature (700 °C) and higher heating rate (10 K/min) generally improved micropore surface areas of beech and spruce biochars. The adsorption capacity of spruce biochar for Cu(II) and Cd(II) increased with higher pyrolysis temperature and lower heating rate (2 K/min) up to 0.14 and 0.12 mmol/g, respectively. In the case of beech biochar, the adsorption capacity for heavy metal ions has no distinct dependence on pyrolysis temperature nor heating rate. The opposite effect of heating rate was found in the case of the methylene blue uptake, better adsorbent can be prepared by pyrolysis with heating rate 10 K/min. The effect of pyrolysis temperature is not clear in this case.

Soil and greenhouse gas responses to biochar additions in a temperate hardwood forest

AbstractBiochar additions can improve soil fertility and sequester carbon, but biochar effects have been investigated primarily in agricultural systems. Biochar from spruce and maple sawdust feedstocks (with and without inorganic phosphorus in a factorial design) were added to plots in a commercially managed temperate hardwood forest stand in central Ontario, Canada; treatments were applied as a top‐dressing immediately prior to fall leaf abscission in September 2011. Forests in this region have acidic, sandy soils, and due to nitrogen deposition may exhibit phosphorus, calcium, and magnesium limitation. To investigate short‐term impacts of biochar application on soil nutrient supply and greenhouse gas fluxes as compared to phosphorus fertilization, data were collected over the first year after treatment application; linear mixed models were used to analyze data. Two to six weeks after treatment application, there were higher concentrations of potassium in spruce and maple biochar plots, and phosphorus in spruce biochar plots, as compared to the control treatment. There were higher concentrations of calcium, magnesium, and phosphorus in the phosphorus plots. In the following spring and summer (9–12 months after treatment application), there were higher soil calcium concentrations in maple biochar plots, and phosphorus plots still had higher soil phosphorus concentrations than control plots. No treatment effects on fluxes of carbon dioxide, methane, or nitrous oxide were detected in the field; however, laboratory incubations after 12 months showed higher microbial respiration in soils from maple biochar plots as compared to spruce biochar, despite no effect on microbial biomass. The results suggest that the most important short‐term impact of biochar additions in this system is the increased supply of the limiting plant nutrients phosphorus and calcium. We expect that larger changes in mineral soil physical and chemical properties will occur when the surface‐applied biochar becomes incorporated into the soil after a few years.