Small Scale Biochar Production Technologies: A Review

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1 Journal Journal of of Emerging Emerging Trends Trends in in Engineering Engineering and and Applied Applied Sciences Sciences (JETEAS) (JETEAS) 11 (2): (2): Scholarlink Research Institute Journals, 2010 jeteas.scholarlinkresearch.org Small Scale Biochar Production Technologies: A Review Odesola, Isaac. F and Owoseni, T. Adetayo Department of Mechanical Engineering, University of Ibadan, Ibadan, Nigeria. Corresponding Author: Odesola, Isaac. F Abstract This paper is set to review the available small scale biochar production technologies. Biochar production technologies are a few of the green technologies that seek to rid the environment of green house gases (GHG). The products of this technology are biochar and biofuels (oil and syngas). Variant methods of this small scale production are known. The use of single (metal) container to two barrels is common, while some units are built of ceramic materials like fired brick. However, there is no published work stating the production of biochar in Nigeria, as at the time of this compilation. Keywords: review, biochar, pyrolysis, GHG, organic materials I TRODUCTIO 7. It often contains large amounts of topsoil. Crop Farming entails extensive cultivation of plants to yield food, feed, or fiber; to provide medicinal or industrial ingredients; or to grow ornamental products. Crop farming developed in ancient times as hunters and gatherers of the Stone Age turned to the cultivation of favored species. Modern crops were gradually derived from their wild ancestors through continual selection for larger seed size, improved fruit, and other desired traits (Pardee, 2008). Soil Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics. (Birkeland, 1999). According to King (2008), Soil is the loose material that covers the land surfaces of Soil Depletion and Use of Fertilizer Soil depletion occurs when the components, which contribute to fertility, are removed and not replaced, and the conditions, which support soil fertility, are not maintained. This leads to poor crop yields. In agriculture, depletion can be due to excessively intense cultivation and inadequate soil management. Depletion may occur through a variety of other effects, including over tillage, which damages soil structure, overuse of inputs such as synthetic fertilizers, and herbicides, which leave residues and buildups that inhibit microorganisms, and salinization of soil. (Wikipedia, 2010). Not all soils have enough nutrients or the right balance of nutrients. In addition, plants remove nutrients from the soil as they grow, so these nutrients must be replaced in order for the soil to remain Earth and supports the growth of plants. productive. For these reasons, gardeners enhance soil Soils vary widely from place to place. Many factors determine the chemical composition and physical structure of the soil at any given location. Fertile Soil Fertile soil has the following properties: by adding fertilizer, a material that contains one or more of the nutrients plants need. (Hynes, 2009) While fertilizers are essential to modern agriculture, their overuse can have harmful effects on plants and crops and on soil quality. In addition, the leaching of 1. It is rich in nutrients necessary for basic plant nutrition, including nitrogen, phosphorus and potassium nutrients into bodies of water can lead to water pollution problems such as eutrophication, by causing excessive growth of vegetation. The use of industrial 2. It contains sufficient minerals (trace elements) for plant nutrition, including boron, chlorine, cobalt, copper, iron, manganese, magnesium, molybdenum, sulfur, and zinc. waste materials in commercial fertilizers has been encouraged in the United States as a means of recycling waste products. The safety of this practice has recently been called into question. Its opponents argue that industrial wastes often contain elements that 3. It contains soil organic matter that improves soil structure and soil moisture retention. poison the soil and can introduce toxic chemicals into the food chain. (Encarta, 2009) 4. Soil ph is in the range 6.0 to 6.8. Biochar 5. Good soil structure, creating well drained soil. Biochar is a fine-grained, highly porous charcoal that 6. A range of microorganisms that support plant growth. helps soils retain nutrients and water. Biochar is found in soils around the world as a result of vegetation fires 150

and historic soil management practices. Intensive study of biochar-rich dark earths in the Amazon (terra preta), has led to a wider appreciation of biochar s unique properties as a soil conditioner.

2 and historic soil management practices. Intensive study of biochar-rich dark earths in the Amazon (terra preta), has led to a wider appreciation of biochar s unique properties as a soil conditioner. (International Biochar Initiative 2008) Figure 1: Sample Biochar Source: Benefits of Biochar As a soil amendment, biochar helps to improve the Earth s soil resources by increasing crop yields and productivity, by reducing soil acidity, and by reducing the need for some chemical and fertilizer inputs. (Glaser et al. 2007) Water quality is improved by the use of biochar as a soil amendment, because biochar aids in soil retention of nutrients and agrochemicals for plant and crop utilization (Lehmann et al. 2003). This reduces leaching and run-off of soil nutrients to ground and surface waters. Biochar improves the soil texture and ecology, increasing its ability to retain fertilizers and release them slowly. It naturally contains many of the micronutrients needed by plants, such as selenium. It is also safer than other "natural" fertilizers such as manure or sewage since it has been disinfected at high temperature, and since it releases its nutrients at a slow rate, it greatly reduces the risk of water table contamination. (Wikipedia 2010) Biochar production and utilization systems differ from most biomass energy systems because the technology is carbon-negative: it removes net carbon dioxide from the atmosphere and stores it, as stable soil carbon sinks. (Lehmann et al. 2006) Other benefits include: Biochar reduces the need for fertilizer, resulting in reduced emissions from fertilizer production. Biochar increases soil microbial life which results in more carbon storage in soil. Because biochar retains nitrogen, emissions of nitrous oxide (a potent greenhouse gas) may be reduced. Turning waste biomass into biochar reduces methane (another potent greenhouse gas) generated by the natural decomposition of the waste. (International Biochar Initiative 2008) Biochar Production The ancient method for producing biochar as a soil additive was the pit or trench method, which created terra preta, or dark soil. While this method is still a potential to produce biochar in rural areas, it does not allow the harvest of either the bio-oil or syngas, and releases a large amount of CO 2, black carbon, and other GHGs (and potentially, toxins) into the air. (Wikipedia, 2010). Biochar production processes can utilize most urban, agricultural or forestry biomass residues, including wood chips, corn stover, rice or peanut hulls, tree bark, paper mill sludge, animal manure, and recycled organics, for instance. ( 2010) Modern method biochar production is sought in pyrolysis. This is done on either small or large scale. Small scale biochar production technologies are replacing the old fashioned way of making biochar. This small scale production allows subsistence farmers to produce small quantities of biochar usable for their farms or garden. Pyrolysis is a form of incineration that chemically decomposes organic materials by heat in the absence of oxygen. Pyrolysis typically occurs under pressure and at operating temperatures above 430 C (800 F). (Wikipedia, 2010). The yield of products from pyrolysis varies heavily with temperature. The lower the temperature, the more char is created per unit biomass. High temperature pyrolysis is also known as gasification, and produces primarily syngas from the biomass (Winsley, 2007). The two main methods of pyrolysis are fast pyrolysis and slow pyrolysis. Fast pyrolysis yields 60% bio-oil, 20% biochar, and 20% syngas, and can be done in seconds, whereas slow pyrolysis can be optimized to produce substantially more char (~50%), but takes on the order of hours to complete. For typical inputs, the energy required to run a fast pyrolyzer is approximately 15% of the energy that it outputs (Laird 2008). Modern pyrolysis plants can be run entirely off of the syngas created by the pyrolysis process and thus output 3 9 times the amount of energy required to run. Alternatively, microwave technology has recently been used to efficiently convert organic matter to biochar on an industrial scale, producing ~50% char. The below diagram depicts the production of biochar using pyrolysis. 151

(about1 in) from the bottom that allow an ample amount of air intake. The smaller one has no hole on it.

The process took one hour, while the produced charcoal was left to cool for one hour. The biochar was then ready. The steps taken by Gunther is depicted in figs. (3-7) shown below.

com An important advantage of biochar is that it can be produced either from small, simple mobile units or from larger, stationary ones.

(Best Energies, 2009) According to Talberg (2009) there are potentially three broad types of pyrolysis systems: Central pyrolysis plants for processing all the biomass in a region.

3 (about1 in) from the bottom that allow an ample amount of air intake. The smaller one has no hole on it. The biomass was stocked into the smaller barrel as tight as possible, with the whole inverted into the larger barrel. The space between the barrels was then filled with wood and ignited. The process took one hour, while the produced charcoal was left to cool for one hour. The biochar was then ready. The steps taken by Gunther is depicted in figs. (3-7) shown below. Figure 2: Simplified pyrolysis process flow diagram Source: An important advantage of biochar is that it can be produced either from small, simple mobile units or from larger, stationary ones. Small-scale systems for biomass inputs of 50 to 1000 kilograms per hour can be used on farms, while large units of up to 8000 kilograms per hour can be operated by large industries. (Best Energies, 2009) According to Talberg (2009) there are potentially three broad types of pyrolysis systems: Central pyrolysis plants for processing all the biomass in a region. Lower-tech pyrolysis kilns for individual farmers or small groups of farmers (these kilns may not include some secondary stages such as the gasification or gas cleanup). Pyrolysis trucks powered by syngas that could be driven around for processing biomass within a region. The biochar and biooil would be transported on the truck back to the customers. Biochar production and utilization systems differ from most biomass energy systems because the technology is carbon-negative: it removes net carbon dioxide from the atmosphere and stores it, as stable soil carbon sinks. (Lehmann et al. 2006) There are two methods to turn wood into charcoal known as the direct and indirect process. The indirect method involves baking the wood in some air tight vessel. This produces the highest yields of charcoal but requires a more elaborate set up. The direct method burns the wood in some container where the amount of oxygen is controlled. (Gary 2007). Folke Gunther (2009) described a two-barrel charcoal retort, used to produce biochar in small quantity. The arrangement consists of two metal barrels, the larger about 20 cm (8 in) wider and 10 cm (4 in) higher than the smaller vessel. In the larger one you air intake is allowed some centimetres Figure 3: The two barrels Source: Figure 4: Small barrel filled with biomass Source: Figure 5: The Complete Arrangement Source: 152

Table 1: Comparative Speed & Capacity of Production Group Drum Diameter (cm) Feed Volume (litres) Cycle Time (hours) F Gunther Holon (Sweden)* 30 40 ~3.0 Figure 6: The Start of the Source : www.

0 * Inner drum diameter of two-drum method-claims minimum GHG/smoke production Figure 7 The Biochar was ready Source : www.holons.se.

The output is one cubic foot of char in less than 30 minutes.

4 Table 1: Comparative Speed & Capacity of Production Group Drum Diameter (cm) Feed Volume (litres) Cycle Time (hours) F Gunther Holon (Sweden)* ~3.0 Figure 6: The Start of the Source : ENC Briggs GBD Wright Lakeland Coppice J P > (2 t dry wood) 72.0 * Inner drum diameter of two-drum method-claims minimum GHG/smoke production Figure 7 The Biochar was ready Source : John Briggs (2009) describes the ENC Consultancy batch process to consume around 6 cubic feet of dry/semi-dry wood and gardening waste. The output is one cubic foot of char in less than 30 minutes. The more awkward materials (brambles, hedge or shrub trimmings, etc) are packed into an open-ended steel cylinder measuring 40 cm in diameter which sits above a hearth made of bricks. Initially, a fire is lit in the hearth with loose twigs laying down a layer of coarse pyrolising material. The pre-packed cylinder is then lowered onto the hearth. Steam is produced and when a lid is placed on the cylinder the back pressure of steam slows down combustion in the hearth. It is important to push down the hot material periodically to maximise packing and therefore charring. Steam evolution is eventually replaced by smoke plus combustible gases. After a few more minutes the process is terminated by quenching with water. The total cycle time is under half an hour and preparation for the next batch can be carried out in parallel with the current batch. He also provides the activities of other groups other than that ENC Consultancy in table (2009) described a carbon zero experimental biochar kiln. It is a simple closed retort kiln built with insulated firebrick. Its enclosure is designed for a 200 liter steel barrel as a retort. The barrel is filled with split wood or other biomass feedstock, covered, and heated from below with a separate wood fire until it reaches pyrolysis temperatures (over 320 C). This unit is shown in fig. 8 Figure 8: Biochar Kiln A batch unit is described on It is a cylindrical unit constructed from steel. It is fired from the top with air supplied from beneath with a blower. It has capacity for 700 litres of input. This unit is shown in figs. (9-10). 153

REFERRE CES Adeyi, O., (2010). Proximate Composition of Some Agricultural Wastes in Nigeria and Their Potential Use in Activated Carbon Production. J. Appl. Sci. Environ. Manage. 14(1):55 58.

9: Schematic of the Batch Unit Source: www.biocharengineering.com Figueira, A., Janick, J., Yadav, M., and BeMiller J., (1994). Cacao Gum: A Potential New Economic Product. Journal paper no. 12,997.

5 REFERRE CES Adeyi, O., (2010). Proximate Composition of Some Agricultural Wastes in Nigeria and Their Potential Use in Activated Carbon Production. J. Appl. Sci. Environ. Manage. 14(1): Anon Pyrolysis. companies/bestpyrolysis.html. Accessed July Birkeland, Peter W., (1999). Soils and Geomorpholog, 3rd Edition. Oxford University Press, New York. Fig. 9: Schematic of the Batch Unit Source: Figueira, A., Janick, J., Yadav, M., and BeMiller J., (1994). Cacao Gum: A Potential New Economic Product. Journal paper no. 12,997. Purdue University Agriculture Experiment Station Glaser, B., Lehmann, J. and Zech, W., (2002). Ameliorating physical and chemical properties of highly weathered soils in the tropics with charcoal-a Review. Biology and Fertility of Soils 35: Hynes, E., (2008). Gardening. [DVD]. Microsoft Encarta Redmond, W.A: Microsoft Corporation. James, A. D. (1983). Handbook of Energy Crops. (Unpublished) Figure 10: Picture of the batch Unit Gary Gilmore (2007) described another two barrel unit. One is used as the retort (bottom) and the other will act as the after burner (top). The retort needs to have a bottom and a lid. The arrangement is shown below in fig. 11. Johannes, L. and Stephen, J., (2009). Biochar for Environmental Management: An Introduction pg. 1 King, C., Soil. Microsoft Encarta (2009) [DVD]. Redmond, WA: Microsoft Corporation. Laird, D. A., (2008). The Charcoal Vision: A Win Win Win Scenario for Simultaneously Producing Bioenergy, Permanently Sequestering Carbon, while Improving Soil and Water Quality. Agronomy. 100: Lehmann, J. and Rondon, M., (2006), Biochar soil management on highly weathered soils in the humid tropics. In Uphoff N (ed.), Biological Approaches to Sustainable Soil Systems, CRC Press, Boca Raton, FL, pp Lehmann, J., et al. (2003). Nutrient availability and Leaching in an Archaeological Anthrosol and a Ferralsol of the Central Amazon basin: Fertilizer, Manure and Charcoal Amendments. Plant and Soil 249: Figure 11: Retort and After Burner Source: Lehmann, J., Gaunt, J., and Rondon, M., (2006), Biochar sequestration in terrestrial ecosystems - A 154

6 Review. Mitigation and Adaptation Strategies for Global Change 11: Leung, A.Y. (1980). Encyclopedia of common natural ingredients used in food, drugs, and cosmetics. John Wiley & Sons. New York. Ofori-Frimpong, K., Afrifa, A.Y., Akrofi and M.R. Appiah. Development of Cocoa Pod Husk Based Compost for Nursing Cocoa Seedlings. Cocoa Research Institute of Ghana (CRIG) P. O. Box 8, Tafo - Akim, Ghana. Pardee, W.D. (2008). Crop Farming. [DVD]. Microsoft Encarta Redmond, WA: Microsoft Corporation. Redmond, W.A. (2008). Fertilizer. [DVD]. Microsoft Encarta Microsoft Corporation. Rondon, M., Ramirez, J.A., and Lehmann, J. (2005). Charcoal Additions Reduce Net Emissions of Greenhouse Gases to The Atmosphere, Proc. 3 rd USDA Symposium on Greenhouse Gases and Carbon Sequestration, Baltimore, USA, March 21-24, 2005, p Sobamiwa, O. and Longe, O.G. (1993). Utilization of Cocoa-Pod Pericarp Fractions in Broiler Chick Diets. Cocoa Research Institute of Nigeria, PMB 5244, Ibadan, Nigeria. Soil Depletion. accessed July 2010 Steiner, C., et al. (2003). Long term effects of manure, charcoal and mineral fertilization on crop production and fertility on a highly weathered Central Amazonian upland soil. Plant and Soil. 291: Winsley, P. (2007). Biochar and Bioenergy Production for Climate Change Mitigation. New Zealand Sci. 64 (5) Yanai et al. (2007). Effects of Charcoal Addition on N 2 O Emissions from Soil Resulting from Rewetting Air-Dried Soil in Short-Term Laboratory Experiments. Soil Science and Plant Nutrition. 53:

Biochar is a high grade of fine-grained, highly porous charcoal that helps soils retain nutrients and water which is put into soil as a soil

. . Biochar is a high grade of fine-grained, highly porous charcoal that helps soils retain nutrients and water which is put into soil as a soil conditioner to promote plant growth, remediate soil contamination,