Dry Biochar Research Articles

The influencing mechanism of O2, H2O, and CO2 on the H2S removal of food waste digestate-derived biochar with abundant minerals

Hydrogen sulfide (H2S) removal has been a significant concern in various industries. In this study, food waste digestate-derived biochar (DFW-BC), a by-product of food waste treatment with abundant minerals, was assessed for removing H2S from different simulated biogas containing oxygen (O2) and carbon dioxide (CO2) and under different moisture (H2O) contents (0% and 20%) of biochar. The influencing mechanisms of the gas conditions combined with the moisture contents were also investigated. The results showed an H2S removal of 1.75 mg g−1 for dry biochar under pure H2S, 4.29 mg g−1 for dry biochar under H2S + O2, 5.29 mg g−1 for humid biochar under H2S, and 12.50 mg g−1 for humid biochar under H2S + O2. For dry DFW-BC, the high Fe content was responsible for the O2 enhancement. In contrast, O2 + H2O activated the catalytic H2S oxidation of the less reactive minerals (mainly Ca). The inhibition of CO2 on H2S adsorption was not obvious for dry DFW-BC; the specific pore structure may have provided a buffer against the physisorption competition of CO2. However, when H2O was present on DFW-BC, the changes in critical biochar properties and sulfur speciation as opposed to that without H2O implied an evident occurrence of CO2 chemisorption. This CO2 chemisorption partially hindered O2 + H2O enhancement, decreasing the H2S removal capacity from 12.50 to 8.88 mg g−1. The negative effect was ascribed to mineral carbonation of CO2, neutralizing the alkaline surface and immobilizing metal oxides, which thus reduced the acceleration in H2S dissociation and activation in catalytic H2S oxidation by O2 + H2O.Graphical

Assessing the Carbon Footprint of Biochar from Willow Grown on Marginal Lands in Finland

Willow biochar can help to sequestrate carbon. However, biomasses should not be grown on arable lands, as it would increase competition with food production and lead to sustainability issues such as increased food prices and decreased food security. The purpose of this study is to calculate the carbon footprint (CF) of willow biochar in Finland and assess the greenhouse gas compensation potential of marginal lands if they are utilized for willow biochar production. The CF of willow biochar is inadequately assessed together with marginal lands in the literature. A cradle-to-grave Life Cycle Assessment (LCA) of willow biochar was conducted. The results were then applied to assess the total CF of marginal lands. It was found that the CF of willow biochar is −1875 kgCO2eq t−1 of dry biochar. Grown on marginal lands in Finland, willow biochar could compensate 7.7% of yearly agricultural greenhouse gas emissions. On buffer zones, willow biochar could also compensate some of the emissions depending on the zone size. The results of the study support current findings of biochar as a carbon negative product. The study also indicates that willow biochar produced in marginal lands can be used to compensate agricultural greenhouse gas emissions to some extent.

Influence of biochar aged in acidic soil on ecosystem engineers and two tropical agricultural plants

Biochar amendment to soil is predicted globally as a means to enhance soil health. Alongside the beneficial result on soil nutrient availability and retention, biochar is presumed to increase soil macro / microbiota composition and improve plant growth. However, evidence for such an effect remains elusive in many tropical agricultural soils. The influence of biochar aged in soil was assessed on soil microbiota, macrobiota (Eudrilus eugeniae), seedling emergence and early plant growth of Oryza sativa and Solanum lycopersicum in tropical agricultural soil, over a 90 d biochar-soil contact time. Results showed negative impacts of increased loading of biochar on the survival and growth of E. eugeniae. LC50 and EC50 values ranged from 34.8% to 86.8% and 0.9–23.7% dry biochar kg−1 soil, over time. The growth of the exposed earthworms was strongly reduced (R2 = −0.866, p < 0.05). Biochar significantly increased microbiota abundance relative to the control soil (p < 0.001). However, fungal population was reduced by biochar addition. Biochar application threshold of 10% and 5% was observed for (O. sativa) and (S. lycopersicum), respectively. Furthermore, the addition of biochar to soil resulted in increased aboveground (shoot) biomass (p < 0.01). However, the data revealed that biochar did not increase the belowground (root) biomass of the plant species during the 90 d biochar-soil contact time. The shoot-to-root-biomass increase indicates a direct toxic influence of biochar on plant roots. This reveals that nutrient availability is not the only mechanism involved in biota-biochar interactions. Detailed studies on specific biota-plant-responses to biochars between tropical, temperate and boreal environments are needed to resolve the large variations and mechanisms behind these effects.

Laboratory Evaluation of the Direct Impact of Biochar on Adult Survival of Four Forest Insect Species

Abstract Application of biochar to managed agricultural and forest ground has been demonstrated to increase soil fertility and productivity and may aid in the retention of H2O and water-soluble nutrients thereby improving water quality while reducing soil acidity and nutrient leaching. However, there have been few studies that examine potential effects of biochar on insect communities. We examined the direct effects of one formulation of dry biochar on survival of four species of common forest insects: major adult workers of the thatch ants, Formica obscuripes Forel (Hymenoptera: Formicidae); adult bark beetles, Ips pini (Say) (Coleoptera: Curculionidae: Scolytinae) and adults of two bark beetle predators, Temnochila chlorodia (Mannerheim) (Coleoptera: Trogossitidae) and Enoclerus sphegeus (Fabricius) (Coleoptera: Cleridae). There was a significant reduction in survival for three of the four species (F. obscuripes, I. pini and T. chlorodia) when exposed to dry biochar in confined arenas. The decreased sur...

Effect of water entrainment by pre-soaked biochar particles on strength and permeability of cement mortar

Water retention by biochar makes it a potential material for soil enhancement. However, its application as an internal curing agent in cementitous matrix is relatively unexplored. This study explores addition of pre-soaked biochar on strength and permeability of cement mortar, subject to moist curing and air curing respectively. Biochar was prepared from mixed wood saw dust at pyrolysis temperature of 300 °C (BC 300) and 500 °C (BC 500) respectively. Biochar particles were saturated with water prior to addition in mortar mix at 2 wt% of cement.Experimental results show that mortar with pre-soaked BC 300 and BC 500 offer 40–50% higher compressive strength at 28-day compared to plain mortar, especially under air curing condition. Similar trend is observed for flexural and split-tensile strength. It is linked to initially low water-cement ratio of mixes with pre-soaked biochar and internal availability of moisture from pores of biochar under external dry condition. Water accessible porosity was reduced by 18–20% due to addition of pre-soaked biochar, that resulted in reduction of sorptivity and depth of water penetration by 55–60%. Overall, significant improvement in mechanical and permeability properties were observed when pre-soaked biochar is used compared to addition of dry biochar in mortar, especially in absence of external moist curing.The internal curing efficiency of pre-soaked biochar on mortar was found to be higher compared to other mixes, which suggests that it can be a potential curing material for cement mortar. Using biochar as additive in cement mortar also ensures higher waste recycling and carbon sequestration in civil infrastructure while improving strength and durability performance.

Fate of Soil Organic Carbon and Polycyclic Aromatic Hydrocarbons in a Vineyard Soil Treated with Biochar.

The effect of biochar addition on the levels of black carbon (BC) and polcyclic aromatic hydrocarbons (PAHs) in a vineyard soil in central Italy was investigated within a two year period. Hydropyrolysis (HyPy) was used to determine the contents of BC (BCHyPy) in the amended and control soils, while the hydrocarbon composition of the semi-labile (non-BCHyPy) fraction released by HyPy was determined by gas chromatography-mass spectrometry, together with the solvent-extractable PAHs. The concentrations of these three polycyclic aromatic carbon reservoirs changed and impacted differently the soil organic carbon over the period of the trial. The addition of biochar (33 ton dry biochar ha(-1)) gave rise to a sharp increase in soil organic carbon, which could be accounted for by an increase in BCHyPy. Over time, the concentration of BCHyPy decreased significantly from 36 to 23 mg g(-1) and as a carbon percentage from 79% to 61%. No clear time trends were observed for the non-BCHyPy PAHs varying from 39 to 34 μg g(-1) in treated soils, not significantly different from control soils. However, the concentrations of extractable PAHs increased markedly in the amended soils and decreased with time from 153 to 78 ng g(-1) remaining always higher than those in untreated soil. The extent of the BCHyPy loss was more compatible with physical rather than chemical processes.

An Efficient Method for Electrical Earth Resistance Reduction Using Biochar

This paper presents a method that treats the soil by replacing a volume of the earthing portion with biochar instead of chemicals. The method contributes to reduce the earth resistance over long periods of time in order to avoid the expensive cost of these elements and their secondary effects. In the proposed method, a volume of soil from an earthing portion of 20 cm in diameter and 1 m deep is replaced with dry biochar. The earthing electrode is driven into this earthing portion. The use of this method significantly reduced the earth resistance with one electrode from 242.0Ω to an average of 26.27 Ω with the Clay sandy soils of the Sahelian zone of Cameroon during the dry season and 2.1 Ω during the rainy season. Furthermore, smaller reductions were achieved when connecting the two such earths in parallel reducing the resistance of clay-sandy soils from 242.0 Ω to 15.2 Ω in the dry season and 1.1 Ω during the raining season.

Lead sorptive removal using magnetic and nonmagnetic fast pyrolysis energy cane biochars

Energy cane biochar (ECBC) was prepared in a 72s fast pyrolysis at 425°C in an auger-fed reactor and ground into 250–600μm diameter particles. This biochar was magnetized by fusing an iron oxide phase to the particles by mixing aqueous biochar suspensions with aqueous Fe3+/Fe2+ solutions, followed by NaOH treatment (MECBC). These biochars were characterized by Raman, FT-IR, X-ray, SEM, SEM–EDX, TEM, EDXRF, pHzpc, elemental analyses, SBET, and magnetic moment determinations. The SBET of energy cane biochar was negligible and increased to 37.13m2/g after Fe3+/Fe2+/NaOH magnetization. The dry biochar contains 18.4% oxygen. This allows swelling in water and permits sorption inside the solid as well as on its pore surfaces, leading to high capacities at low surface areas. Maximum lead removal occurred at pH 4–5. Sorption isotherms exhibited increasing lead removal (Q0, mg/g) as temperature increased for nonmagnetic [Q025°C=45.70; Q035°C=52.01 and Q045°C=69.37] and magnetic [Q025°C=40.56; Q035°C=51.17 and Q045°C=51.75] biochars. Second order kinetics best fit the lead removal data. Furthermore, magnetic energy cane biochar was easily manipulated by low external magnetic field, thereby, allowing its easy recovery for further recycling and replacement from water. ECBC and MECBC were also successfully applied for Pb2+ removal from contaminated ground water. Therefore, both chars can be used as potential green low cost sorbents for lead remediation to replace commercial activated carbon.

Anaerobic digestion and gasification coupling for wastewater sludge treatment and recovery

Sewage sludge management is an energy intensive process. Anaerobic digestion contributes to energy efficiency improvement but is limited by the biological process. A review has been conducted prior to experimentation in order to evaluate the mass and energy balances on anaerobic digestion followed by gasification of digested sludge. The purpose was to improve energy recovery and reuse. Calculations were based on design parameters and tests that are conducted with the anaerobic digester of a local wastewater treatment plant and a small commercial gasification system. Results showed a very significant potential of energy recovery. More than 90% of the energy content from sludge was extracted. Also, approximately the same amount of energy would be transferred in both directions between the digester (biogas) and the gasifier (thermal energy). This extraction resulted in the same use of biogas as the reference scenario but final product was a totally dry biochar, which represented a fraction of the initial mass. Phosphorus was concentrated and significantly preserved. This analysis suggests that anaerobic digestion followed by dehydration, drying and gasification could be a promising and viable option for energy and nutrient recovery from municipal sludge in replacement of conventional paths.

Comparison of sewage sludge- and pig manure-derived biochars for hydrogen sulfide removal

Biochars derived from pig manure and sewage sludge were evaluated for their abilities to remove hydrogen sulfide (H2S) from gas phase. The pig manure biochar had higher capacities for H2S sorption than sewage sludge biochar in both dynamic and static systems, and moisture improves H2S removal. Increasing the biochar moisture to 25 wt% and 100 wt% in the static system increased the pig manure biochar removal capacities by 15.9% and 58.9%, respectively, compared to the dry biochar (0 wt% moisture). The sewage sludge biochar similarly increased the removal by 1.04 and 3.30 times for 25 wt% and 100 wt% moisture, respectively. The catalytic conversion to elemental S0 and SO42− was the main route of H2S removal. The complete oxidation of H2S into SO42− mainly occurred on the biochar surface, while H2S underwent incomplete oxidation into elemental S0 in the biochar pores. The SO42− was the dominant form in both biochars, especially for the pig manure biochar which contained 53.9% of the total sulfur at 100 wt% moisture. The SO42− was mainly present as CaSO4 precipitate in the sewage sludge biochar, while SO42− in the pig manure biochar was mostly soluble (K, Na)2SO4. The results indicated the waste biomass can be converted into value-added biochar as a sorbent for H2S, especially at high moisture that promotes complete oxidation of H2S into SO42−. Strong alkalinity and rich inorganic minerals originated in the biochar play an important role in its high H2S sorption ability and the final sulfur forms.

Earthworm avoidance of biochar can be mitigated by wetting

Biochar has a great potential for enhancing soil fertility and carbon sequestration while enabling beneficial waste disposition. Because of the potential for widespread application, it is essential to proactively assess and mitigate any unintended consequences associated with soil biochar amendment. We conducted soil avoidance tests, growth and reproduction tests, and oxidative stress assays with the earthworm Eisenia foetida to assess the potential toxicity of soil amended with biochar produced from apple wood chips. Earthworms avoided soils containing 100 and 200 g/kg dry biochar at statistically significant levels ( p < 0.05), and after 28-day incubation, these earthworms lost more weight than those in control (unamended) soil. However, biochar did not affect the reproduction of earthworms. We investigated whether the observed avoidance was due to nutrition deficiency, desiccation, or the presence of toxic polynuclear aromatic hydrocarbons (PAHs) formed during biochar production by pyrolysis. Nutrition deficiency was excluded by the lack of earthworm avoidance to soil amended with nutrient-deficient sand instead of biochar. Although traces of PAH were detected in the tested biochar (e.g., 25.9 μg/kg fluorene, 3290 μg/kg naphthalene, and 102 μg/kg phenanthrene), the lack of lipid peroxidation and no increase in superoxide dismutase activity in biochar-exposed earthworms suggests that presence of toxic compounds was not a likely reason for avoidance. Furthermore, wetting the biochar to its field capacity resulted in statistically undetectable avoidance relative to control soil, indicating that insufficient moisture could be a key factor affecting earthworm behavior in soil amended with dry biochar. To avoid desiccation of invertebrates and enable their beneficial ecosystem services, we recommend wetting biochar either before or immediately after soil application.