Biochar Technology Research Articles

A Dialogue on Perspectives of Biochar Applications and Its Environmental Risks

Biochar presents great promise as a technology that makes a substantial contribution in various fields of environmental research. However, existing knowledge is still uneven and limited in terms of its effective utilization and field application. In this review, a comprehensive discussionof biochar technology is presentedwith respect to three main aspects:(1) biochar stability; (2) application in soil for conditioning, remediation, and GHG reduction; and (3) biochar sustainability and its environmental impacts. Biochar is a highly stable and slow-mineralizing product; therefore, its application promotes agricultural productivity by providingan efficient nutrient balance and soil fertility, and by restricting the loss of nutrients due to its surface sorption capacity. Moreover, it contributes significantly to the reduction of greenhouse gas emissions from the soil through carbon sequestration. The high adsorption capacity of biochar aids in removing contaminants from soil, thus assisting in the restoration of contaminated sites.Nevertheless, biochar poses certain negative impacts to the environment as well. A few studies have reported that biochar could release organic and inorganic contaminants such as phenol, PAHs, POPs, dioxins, furans, and heavy metals into the soil, altering the soil productivity and soil biota. In certain circumstances, biochar is also responsible for emission of CO2 from soil due to the priming effect. However, the effect of biochar in soil varies widely depending upon ecological conditions, the pyrolysis process, and the feedstock materials. Overall, this review aims to help in evaluating and addressing the mechanistic understanding of biochar functions in the environment and encouraging awareness of the need forfuture research to counteract its negative environmental consequences.

Sorption of naphthalene and its hydroxyl substitutes onto biochars in single-solute and bi-solute systems with propranolol as the co-solute

The sorption of naphthalene and its hydroxyl-substituted compounds onto two biochars that were produced at different temperatures was studied. The influences of propranolol as a co-solute and solution pH on the sorption were investigated. The sorption capacities of 1-naphthol and 4-nitro-1-naphthol on the biochar with a pyrolytic temperature of 200°C (BC200) were greater compared to naphthalene. This occurred because the substitution of hydroxyl- and nitro-groups on the aromatic ring enhanced surface adsorption, e.g. hydrogen bond and π-π electron donor-acceptor interaction, while the hydroxyl in 1-naphthalenemethanol did not show the promoting effect. The sorption on the biochar with a pyrolytic temperature of 700°C (BC700) followed a different sequence of 4-nitro-1-naphthol<1-naphthalenemethanol<1-naphthol<naphthalene, which was determined by the hydrophobicity and molecular volume of the sorbates, indicating the dominance of hydrophobic partition and pore-filling in the adsorption on BC700. The co-existence of propranolol promoted the surface hydrophobicity of BC200, which led to an enhancement in the sorption of naphthalene and 1-naphthalenemethanol. Propranolol prohibited the sorption of 1-naphthol by competing for the mutual available surface adsorption sites. The ion-pair reaction between anionic 4-nitro-1-naphthol and cationic propranolol increased the sorption of 4-nitro-1-naphthol. On BC700, propranolol generally prohibited the sorption of the tested sorbates mainly due to competition and pore-blocking. The influence of pH was complicated in both single-solute and bi-solute systems. It simultaneously affected the surface charge of biochars and the form of the tested compounds, which led to the shifting of sorption mechanisms. The finding will shed light on the suitable application of biochar technology.

Biochar provides a safe and value-added solution for hyperaccumulating plant disposal: A case study of Phytolacca acinosa Roxb. (Phytolaccaceae)

In this work, an innovative approach using biochar technology for hyperaccumulator disposal was developed and evaluated. The heavy metal enriched P. acinosa biomass (PBM) was pyrolyzed to produce biochar (PBC). Both PBM and PBC were characterized with X-ray diffraction (XRD) for crystal phases, scanning electron microscopy (SEM) for surface topography, and analyzed for elemental composition and mobility. The results revealed that whewellite, a dominant crystal form in biomass, was decomposed to calcite after pyrolysis. Elemental analysis indicated that 91–99% total non-volatile elements in the biomass were retained in the biochar. The toxicity characteristic leaching procedure (TCLP) results revealed that 94.6% and 0.15% of total Mn was extracted for biomass and biochar, respectively. This suggests that mobility and bioavailability of Mn in biochar was much lower relative to pristine biomass. Batch sorption experiment showed that excellent removal of aqueous silver, lead, cadmium, and copper ions can be achieved with PBC. Findings from this work indicated that biochar technology can provide a value-added solution for hyperaccumulator disposal.

Changes in microbial biomass and the metabolic quotient with biochar addition to agricultural soils: A Meta-analysis

Biochar has been increasingly recommended for world agriculture, but the effects on microbial activities in agricultural soils has not yet thoroughly assessed. In this study, using a meta-analysis of experiment data retrieved from literature published up to March 1, 2015, changes were examined in microbial biomass and soil respiration in agricultural soils with biochar addition. Microbial responses to biochar addition were quantified in soil respiration quotient (RQ), microbial quotient (MQ) and metabolic quotient (qCO2) and their differences were evaluated between with and without biochar addition, and among groups of biochar production conditions and experiment conditions. There was an overall increase by 25% in soil microbial biomass carbon (SMBC) and nitrogen (SMBN) but a decrease by 13% in qCO2, under biochar compared to the control. Whereas, microbial biomass carbon was increased by 26% but total soil CO2 production unchanged, across all short term experiments up to 6 months following a single biochar addition. A significant reduction (by <20%) in qCO2 was found under crop residue and manure biochars in term of feedstock, and biochars pyrolyzed at high temperature over 500°C in term of pyrolysis temperature. Whereas, the reduction was great (by over 30%) both in clay soils and in neutral soils but moderate (by 15%) in soil organic carbon (SOC) depleted soils, respectively in terms of soil texture, reaction and SOC level. Thus, soil conditions exerted great impacts on microbial metabolic quotient changes compared to biochar conditions. Nevertheless, microbial responses to biochar addition to agricultural soils were much uncertain with respect to both biochar and experiment conditions. Long term field experiments are still deserved to monitor soil microbial processes as long as sustainable soil managements are concerned with biochar technology in agriculture.

Biochar Technology as a Go Green Movement in Indonesia

Charcoal has long been known by the community in its use either as energy sources or for agriculture/forestry-related aspects. Beginning from the discovery of the so-called Terra Preta, the role of charcoal in improving soil fertility and enhancing its productivity at agriculture as well as forestry lands has attracted remarkable attention internationally ever since. Raw material for charcoal can be wood or other ligno-cellulosic stuffs (e.g. coconut shells, oil-palm shells, rice husks, wood sawdust, nut shells, etc). Technology in charcoal manufacture commonly employed by the community comprises heaping-kiln, drum kiln, and dome-shaped kiln systems. Such manufacture technology is simply carbonizing the ligno-cellulosic stuffs inside the kiln into charcoal. The charcoal yield usually ranges about 20-25% (w/w), implying that as much 75-80% of the stuffs is lost as smoke that further escape to the air. Environment concerns arise since such escaped smoke can pollute the atmosphere and hence contribute to the global warming. Measures are urgently needed to reduce the amount of such escapes among others, as developed by the Center for Research and Development on Forestry Engineering and Forest Products Processing (CRDFEFPP, Indonesia) by cooling the smoke, during the carbonization of ligno-cellulosic stuffs, thereby condensing it into liquid smoke (popularly called as wood vinegar). Through intensive and tedious researches, it is found out that the wood vinegar (as charcoal by-product) could effectively function as bio-pesticides and bio-fertilizers. Meanwhile, application of charcoal to the seedlings of forestry plant species reveals positive responses as shown by the increase in biomass weight of those plants on other positive plant-growth aspects (e.g. stem height and diameter). Likewise, the use of charcoal combined with compost (i.e. organic fertilizer that results from bio-conversion of biomass stuffs) could enhance as much 2-3 times the production of vegetables plants as the control (untreated plants). This in all strongly indicates the charcoal and wood-vinegar manufacture entirely called as essentially the bio-char technology, can convert biomass stuffs (previously regarded as not or less useful) into value-added or more useful products (charcoal and wood vinegar).

A review of biochar as a low-cost adsorbent for aqueous heavy metal removal

ABSTRACTAs a low-cost adsorbent, biochar can be used as a low-cost adsorbent for wastewater treatment, particularly with respect to treating heavy metals in wastewater. A number of studies have demonstrated effective removal of heavy metals from aqueous solutions by biochar and, in some cases, proven the superiority of biochars to activated carbons. Among several factors affecting the sorption ability of biochars, feedstock materials play a significant role. This review incorporates existing literature to understand the overall sorption behavior of heavy metals on biochar adsorbents. Depending on the biochar type, heavy metal can be removed by different mechanisms such as complexation, physical sorption, precipitation and electrostatic interactions. Mathematical sorption models can be used to understand the efficiency of biochar at removing heavy metals, and promote the application of biochar technology in water treatment.

SMART biochar technology—A shifting paradigm towards advanced materials and healthcare research

Biochar, produced through pyrolysis of biomass under low or no oxygen conditions, has found a wide range of applications from soil fertility improvement to removal of contaminants. Initial interest in biochar is to use it as a means to capture carbon dioxide from the atmosphere; however, recent developments are seeing biochar being applied in engineering, and health care and life sciences, some of those applications have large potentials for rapid commercialization. We expect a paradigm shift towards the development of the next generation of biochar with applications in a range of new fields.

Prospects of Biochar Technology in China Based on SWOT Analysis

Application of biochars to soils is suggested as an effective way for improving soil quality and mitigating greenhouse gas emissions, which has generated great interest for scientists and policy makers. However, studies of biochar mainly focused on the basic mechanisms of interactions between biochars and soils. The evaluation of macro development prospect of biochar technology in China is much limited. The method of SWOT (Strength, Weakness, Opportunity and Threat) analysis was used to evaluate the prospect of biochar technology in China. The results indicate that biochar technology has great advantages and potentials in carbon emission reduction, agricultural production improvement, environmental protection and the energy structure optimization. Still, some weaknesses and environmental risk also need to be carefully considered. Finally, some suggestions for the application and promotion of biochar technology in China were provided for development of biochar industry in China.

Cost‐benefit analysis of using biochar to improve cereals agriculture

AbstractBiochar has received considerable scientific attention in the past decade as a possible method for carbon storage and increasing agricultural yields. Despite this promise, however, economic assessments of biochar are yet to definitively establish the value of the technology, primarily due to discrepancy between observed short‐term agronomic benefits and expectations of biochar as a lasting soil improver. This study investigated the economic value of biochar as an agricultural technology for long‐term improvement of arable farming. From presently available field trial data, the costs and benefits of using biochar technology to enhance cereals agriculture were evaluated in two generalized geo‐economic agricultural scenarios: North‐Western Europe (NWE) and Sub‐Saharan Africa (SSA). Cost models were developed to estimate the total cost of biochar from initial biomass feedstock acquisition to final soil application for each agricultural setting. Benefits of biochar application were estimated by statistical meta‐analysis of crop yield data from published biochar field trials to find the increase in cereal grain yield attributable to biochar application for both NWE (+0.07 to +0.28 t ha−1 yr−1) and SSA (+0.18 to +1.00 t ha−1 yr−1). The grain yield improvement from a one‐time biochar application was assumed to persist without decay for an independently varying time period, and the increase in grain production then monetised using projected future commodity prices. The Net Present Value (NPV) of applying biochar was then calculated by setting present total costs against present total benefits as a function of biochar performance longevity. Biochar application was found to carry a positive NPV for cereal cropping in SSA in several scenarios where the duration of the biochar yield effect was assumed to extend 30 years into the future. Conversely, NWE biochar scenarios were all found to have negative NPVs even when the benefits time span was indefinitely stretched.

Opportunities and constraints for biochar technology in Australian agriculture: looking beyond carbon sequestration

The application of biochar technology for soil amendment is largely based on evidence about soil fertility and crop productivity gains made in the Amazonian Black Earth (terra preta). However, the uncertainty of production gains at realistic application rates of biochars and lack of knowledge about other benefits and other concerns may have resulted in poor uptake of biochar technology in Australia so far. In this review, we identify important opportunities as well as challenges in the adoption of biochar technology for broadacre farming and other sectors in Australia. The paper highlights that for biochar technology to be cost-effective and successful, we need to look beyond carbon sequestration and explore other opportunities to value-add to biochar. Therefore, some emerging and novel applications of biochar are identified. We also suggest some priority research areas that need immediate attention in order to realise the full potential of biochar technology in agriculture and other sectors in Australia.

The promise [and uncertainties] of Biochar

The promise [and uncertainties] of Biochar

International Partnership Helping to Bring Appropriate Biofuel Technology to Rural Cameroon

In May 2012, a group of chemical and mechanical engineering students from the newly established [University Name] Appropriate Technology and Sustainability [Identifying Acronym] undergraduate research group embarked on a 10 day visit to Bangang Village, Cameroon in West Africa to implement a multidisciplinary engineering service-based project to develop appropriate, sustainable biodiesel and biochar technology for use by local villagers. The participating students had worked on this design project both as part of their capstone design course in both Chemical and Mechanical Engineering and as part of a special elective that included an embedded study abroad component. Poverty and rapid population growth have led to the accelerated destruction of natural resources throughout the developing world, particularly West Africa. The purpose of this project was not only to introduce students to the concepts of sustainability, service based learning and appropriate technology, but to get them beyond the textbooks and laboratories and solve real problems that impact real people around the world.

Synthesis, characterization, and environmental implications of graphene-coated biochar

Biochar has attracted much research attention recently because of its potential applications in many environmental areas. In this work, the biochar technology was combined with the emerging graphene technology to create a new engineered graphene-coated biochar from cotton wood. The biomass feedstock was first treated with graphene/pyrene‐derivative and was then annealed at 600°C in a quartz tube furnace under N2 environment. Laboratory characterization with different microscopy and spectrometry tools showed that the graphene sheets were “soldered” by the pyrene molecules on the biochar surface during the annealing process. Thermogravimetric analysis showed that the graphene “skin” could improve the thermal stability of the biochar, making the engineered biochar a better carbon sequester for large scale land applications. Batch sorption experimental results indicated that the graphene-coated biochar has excellent adsorption ability of polycyclic aromatic hydrocarbons (PAHs) with a maximum methylene blue adsorption capacity of 174mgg−1, which is more than 20 times higher than that of the unmodified cotton wood biochar and comparable to those of some physically or chemically activated carbons. The enhanced adsorption of methylene blue on the graphene-coated biochar is mainly controlled by the strong π–π interactions between aromatic molecules and the graphene sheets on biochar surface. It is anticipated that this novel, facile, and low-cost method can be expanded to other carbon-rich materials to create engineered biochar for various environmental applications.

Pyrolysis for Biochar Purposes: A Review to Establish Current Knowledge Gaps and Research Needs

According to the International Biochar Initiative (IBI), biochar is a charcoal which can be applied to soil for both agricultural and environmental gains. Biochar technology seems to have a very promising future. Nevertheless, the further development of this technology requires continuing research. The present paper provides an updated review on two subjects: the available alternatives to produce biochar from a biomass feedstock and the effect of biochar addition to agricultural soils on soil properties and fertility. A high number of previous studies have highlighted the benefit of using biochar in terms of mitigating global warning (through carbon sequestration) and as a strategy to manage soil processes and functions. Nevertheless, the relationship between biochar properties (mainly physical properties and chemical functionalities on surface) and its applicability as a soil amendment is still unclear and does not allow the establishment of the appropriate process conditions to produce a biochar with desired characteristics. For this reason, the need of enhancing the collaboration among researchers working in different fields of study is highlighted: production and characterization of biochar on one hand, and on the other measurement of both environmental and agronomical benefits linked to the addition of biochar to agricultural soils. In this sense, when experimental results concerning the effect of the addition of biochar to a given soil on crop yields and/or soil properties are published, details regarding the properties of the used biochar should be well reported. The inclusion of this valuable information seems to be essential in order to establish the appropriate process conditions to produce a biochar with more suitable characteristics.

Biochar as a Geoengineering Climate Solution: Hazard Identification and Risk Management

Biochar technology has been proposed as a geoengineering solution that has potential to actively reduce the atmospheric concentrations of greenhouse gases and enhance the sustainability of agriculture. The magnitude of the technologies’ net benefit must be considered in relation to the associated risks. Hazards posed by biochar technology need to be managed to a level that the resulting risks are deemed acceptable by society; identification of hazards is an essential first step. Effectively implemented risk management and sustainability guidelines, driven by informed policy directives, will result in biochar technology being an important tool for environmental and atmospheric greenhouse gas management.

Biochar: Carbon Mitigation from the Ground Up

As multibillion-dollar projects intended to sequester carbon dioxide (CO2) in deep geologic storage continue to seek financial support, the fertile black soils in the Amazon basin suggest a cheaper, lower-tech route toward the same destination. Scattered patches of dark, charcoal-rich soil known as terra preta (Portuguese for “black earth”) are the inspiration for an international effort to explore how burying biomass-derived charcoal, or “biochar,” could boost soil fertility and transfer a sizeable amount from the atmosphere into safe storage in of CO2 topsoil. Although burial of biochar is just beginning to be tested in long-term, field-scale trials, studies of Amazonian terra preta show that charcoal can lock up carbon in the soil for centuries and improve soil fertility. Charcoal is made by heating wood or other organic material with a limited supply of oxygen (a process termed “pyrolysis”). The products of the pyrolysis process vary by the raw material used, burning time, and temperature, but in principle, volatile hydrocarbons and most of the oxygen and hydrogen in the biomass are burned or driven off, leaving carbon-enriched black solids with a structure that resists chemical and microbial degradation. Christoph Steiner, a research scientist at the University of Georgia, says the difference between charcoal and biochar lies primarily in the end use. “Charcoal is a fuel, and biochar has a nonfuel use that makes carbon sequestration feasible,” he explains. “Otherwise there is no difference between charcoal carbon and biochar carbon.” Charcoal is traditionally made by burning wood in pits or temporary structures, but modern pyrolysis equipment greatly reduces the air pollution associated with this practice. Gases emitted from pyrolysis can be captured to generate valuable products instead of being released as smoke. Some of the by-products can be condensed into “bio-oil,” a liquid that can be upgraded to fuels including biodiesel and synthesis gas. A portion of the noncondensable fraction is burned to heat the pyrolysis chamber, and the rest can provide heat or fuel an electric generator. Pyrolysis equipment now being developed at several public and private institutions typically operate at 350–700°C. In Golden, Colorado, Biochar Engineering Corporation is building portable $50,000 pyrolyzers that researchers will use to produce 1–2 tons of biochar per week. Company CEO Jim Fournier says the firm is planning larger units that could be trucked into position. Biomass is expensive to transport, he says, so pyrolysis units located near the source of the biomass are preferable to larger, centrally located facilities, even when the units reach commercial scale.