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International Journal of & World Ecology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tsdw20 use in and -based agro- ecosystems for increasing mitigation and adaptation Ilan Stavi a a Dead Sea and Arava Science Center, Ketura, 88840, Israel Published online: 06 Mar 2013.

To cite this article: Ilan Stavi (2013) Biochar use in forestry and tree-based agro-ecosystems for increasing climate change mitigation and adaptation, International Journal of Sustainable Development & World Ecology, 20:2, 166-181, DOI: 10.1080/13504509.2013.773466 To link to this article: http://dx.doi.org/10.1080/13504509.2013.773466

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Biochar use in forestry and tree-based agro-ecosystems for increasing climate change mitigation and adaptation Ilan Stavi* Dead Sea and Arava Science Center, Ketura, 88840, Israel

(Received 9 September 2012; final version received 2 February 2013)

This study reviews the potential use of biochar as soil amendment in , , , fruit tree orchards, and bio-energy . Implementing this practice could sequester large amounts of carbon (C) over the long-term, potentially offsetting anthropogenic emissions of carbon dioxide, and mitigating climate change. On a global scale, this practice could sequester between 2 and 109.2 Pg biochar-C in 1.75 billion ha of degraded and deforested lands and agroforestry systems. An additional considerable amount could be sequestered in the soil of fruit tree orchards and bio-energy plantations. The anticipated improvement in the quality of the biochar-amended soils is expected to enhance resilience to these land uses, increasing their adaptation capacity to climate change. Yet, specific questions still need to be addressed, for example, the impact of biochar on the availability of nitrogen and potassium for plants in acidic soils and under humid conditions, as well as the impact of biochar on soil and in alkaline soils and under Mediterranean or drier conditions. Also, a full assessment of health hazards and environmental risks related to the production of biochar and its application in soil is required. Other questions relate to the environmental and economic costs of biochar application. Therefore, life cycle assessments and economic calculations should be conducted on a site-specific basis and include the practices of feedstock collection, transportation, processing, and spreading. International actions should regulate biochar practice as an eligible means for funding under the C finance mechanism. Specifically, payments should be provided to landowners for accomplishing ecosystem services. Keywords: ; Clean Development Mechanism (CDM); environmental regulations; land restoration; Reducing Emissions from and Degradation (REDD)

Introduction function much like natural disturbances in their effect on cover almost 4 billion ha or 30% of the global a ’s C balance (Conant 2011). land area, and are considered the major terrestrial regula- Land-use change results in a considerable decrease in tor of the carbon (C) cycle. Natural forests are widespread forest area. Between 2000 and 2005, the global deforesta- −1 throughout several biomes, including the equatorial, tropi- tion rate was 12.9 million ha year , mainly as a result cal, Mediterranean, warm temperate, temperate, and boreal of converting forests to agricultural land, but also due to (Easterling et al. 2007; Nabuurs et al. 2007). The natu- the expansion of settlements, infrastructure, and unsus- ral forests are generally described as evergreen broadleaf, tainable practices (Nabuurs et al. 2007). Forest evergreen needleleaf, deciduous broadleaf, deciduous degradation could be somewhat reversed through imple- needleleaf, or mixed (De Fries et al. 1998). A report pub- menting forestry projects. In 2005, intensively managed ∼ lished by the FAO estimated global forests’ C pools as forest plantations comprised 4% of the global forest area. Downloaded by [University of Wyoming Libraries] at 12:33 05 October 2013 221 Pg in above-ground and 61 Pg in below- The area of this has been rapidly growing, with ground biomass, yielding together a total biomass-C pool an annual increase of between 2.5 (Easterling et al. 2007) of ∼282 Pg. According to this report, global forests’ C and 3.5 million ha (Niles et al. 2002). Due to forestry pool in dead , litter, and the upper 30-cm soil depth efforts, landscape restoration, and natural expansion of accounts for 39, 25, and 287 Pg, respectively. Therefore, forests that, to some extent, reverse the total loss of forest the total forests’ C pool throughout the globe was estimated lands, the most recent estimation of global net loss of forest −1 in 2005 as ∼633 Pg (Marklund & Schoene 2006). In undis- is 7.3 million ha year (Nabuurs et al. 2007). A recently turbed forests, the C balance has a tendency toward slight published synthesis study compared the C sequestration accumulation as its uptake through photosynthesis exceeds capacity of primary and secondary natural forests to that of losses from respiration. However, net C uptake is offset afforestation and reforestation plantations. Overall, com- by disturbances, such as wildfires, droughts, or diseases, pared with the natural forests, the plantations were reported which periodically lead to substantial losses from both to have 11% less above-ground biomass. Also, fine root vegetation and soil. Also, anthropogenic activities often biomass, soil organic C (SOC) concentration, and soil

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© 2013 Taylor & Francis International Journal of Sustainable Development & World Ecology 167

microbial C concentration were reported to be, respec- nitrogen (N) content are greater in pine chips than in poul- tively, 66%, 32%, and 29% lower in plantations than in try litter-derived biochar (Gaskin et al. 2008). A higher natural forests (Liao et al. 2010). In addition, Liao and col- pyrolysis temperature results in lower biochar mass recov- leagues reported 22%, 20%, and 26% smaller available N, ery, greater surface area, elevated pH, higher ash content, P and K, respectively, in the soil of plantations than in the minimal total surface charge (Novak et al. 2009), and natural forests. lower cation exchange capacity (CEC) (Kloss et al. 2012). The productivity of forests and climatic changes are Removal of volatile compounds at higher pyrolysis tem- closely interrelated. It is foreseen that the magnitude, peratures also cause biochars to have higher C content and frequency, and duration of extreme climatic events will lower hydrogen (H) and O content (Novak et al. 2009). The increase as the Earth’s atmosphere warms. From 2001 to production of biochar is inexpensive and can be practiced 2010, global temperatures averaged 0.46◦C above the by low-income populations (Stavi & Lal 2013). According 1961–1990 average. Recent warming has been especially to the International Biochar Initiative, 154 biochar projects strong in , parts of Asia, and parts of the Arctic. were carried out in 43 developing countries in 2011. These Temperatures recorded during 2001–2010 in the Saharo- projects took place within a range of operational and func- Arabian region, east Africa, central Asia, Greenland, and tional scales, including on household (26%), farm (41%), Arctic Canada have all been 1.2–1.4◦C above the long- village (12%), cooperative (11%), and regional (10%) lev- term average and 0.7–0.9◦C warmer than in any previous els. Feedstocks contained a range of organic materials decade (WMO 2011). It is acknowledged that the rising including timber mill waste, livestock manure, concentrations of atmospheric carbon dioxide (CO2)are , field stover, and fruit waste. The biochar produc- expected to have a ‘fertilization effect’ on forests, poten- tion scale varied from small to large, and the technologies tially increasing their production capacity (Beedlow et al. varied from batch retort kiln to continuous process kiln 2004). However, forest C sinks are unlikely to persist (Kelpie 2011). indefinitely, and therefore, continued warming will proba- In spite of the several agronomic and environmen- bly diminish and potentially even override the fertilization tal advantages offered by biochar, its production and use effect (Gullison et al. 2007). Together with increasing may impose specific environmental risks, as well as occu- air pollution and decreasing nutrient availability for plant pational and health hazards. For example, biochars can uptake, the total impact on forests productivity is unclear. potentially contain toxic compounds, such as heavy met- Global warming is also expected to exacerbate risks to als, dioxins, and polycyclic aromatic hydrocarbons (PAHs). forests from ozone (O3), because hot weather and high The occurrence of these contaminants in biochars is likely atmospheric pressure promote its formation. Moreover, to derive from either contaminated feedstocks or the use of increased fossil fuel use will probably increase the produc- processing conditions that foster their formation (Verheijen tion of O3-forming air pollutants, resulting in decreased C et al. 2010). To some extent, the composition of PAHs can sequestration capacity in biomass and soil (Beedlow et al. be controlled through modifying the pyrolysis’ temperature 2004). While a system’s productivity affects its ability to (Kloss et al. 2012). Moreover, it seems that tight control accumulate C, its resilience is largely the result of its capac- on the feedstock materials and pyrolysis conditions might ity to cope with degraded physical conditions (Kandji et al. substantially reduce PAH levels, as well as the emissions 2006). The outcome is a close association between the of dioxins and particulate matter associated with biochar mitigation and adaptation capacities of forest ecosystems. production (Verheijen et al. 2010). Biochar is the by-product of the C-negative pyrolysis Despite the prevalent use of biochar in agriculture, technology for the production of bio-energy from organic very few studies have examined its utilization in forestry materials. The process is conducted under complete or par- and other tree-based agro-ecosystems. Therefore, this

Downloaded by [University of Wyoming Libraries] at 12:33 05 October 2013 tial exclusion of oxygen (O) and relies on capturing the off- paper aims to examine the possibility of augmenting gases from thermal decomposition of the organic materials C sequestration in forestry and other tree-based agro- (Lehmann 2007). After application in soil, the high poros- ecosystems by applying this stable C-based soil amend- ity of biochar and its negative charge increases the soil’s ment to soils. Also, since this management practice is water-holding capacity and nutrient retention, augmenting expected to improve soil quality and fertility, this study availability of water and nutrients for plant uptake. Indeed, examines its potential to increase forests’ resilience, or application of biochar in soil was reported to increase its adaptation capacity, to climate change. In this regard, four physical and chemical qualities, resulting in greater net major pathways were previously mentioned in which C primary productivity (NPP) of the agro-ecosystem (Laird emissions are mitigated through forestry activities: (i) an et al. 2010). At the same time, the recalcitrant nature increase of forested land area (ii); an increase in the C den- of biochar considerably decreases its decomposition by sity of existing forests (iii); expanded use of forest products microorganisms and enables the long-term sequestration to achieve a sustainable reduction of fossil fuel use; and of C in soil (Lehmann 2007). The biochar’s physical and (iv) reduction of emissions from deforestation and land chemical characteristics are determined by feedstock type degradation (Canadell & Raupach 2008). Either directly or and pyrolysis temperature. For example, higher salt and indirectly, this review addresses each of these pathways. ash contents are expected in wheat straw than in wood- More specifically, the objectives of this review were (1) to derived biochar (Kloss et al. 2012), and C content and raise awareness of the potential of biochar applications as 168 I. Stavi

a soil amendment in these land uses, in order to encourage N and potentially susceptible to microbial decomposition. research and development of this management practice; Nocentini and colleagues reported that wood-derived char- (2) to highlight the major challenges in implementing such coal was largely prevalent in the largest fraction of >2 mm, projects; and (3) to demonstrate the need for international while pine needles and herbs were more dominant in regulations to accomplish widespread implementation of the smallest fractions. Santín et al. (2012) reported that this practice. extreme fires in mixed-species eucalypt forests and tem- perate in Victoria, Australia, converted tree- biomass into ash, resulting in deposits of between 4.8 and Deforestation and the C cycle 8.1 Mg C ha−1 on the forest floor. Yet, while some of the Recent estimations revealed that deforestation is the sec- ash remained on-site, much of it was subsequently redis- ond largest anthropogenic source of CO2 in the atmosphere tributed, accumulating in foot slopes and depressions, or after fossil fuel combustion. Cumulative emissions from entering fluvial systems and forming a part of aqueous deforestation and account for between deposits. Also, Wardle et al. (2008) reported that during 12% (van der Werf et al. 2009) and 20% (Gullison et al. a 10-year study of the Swedish boreal, the loss of forest 2007) of total emissions. According to the more con- humus increased when mixed with through either servative estimation, these emissions yielded ∼1.2 Pg C respiration or leaching of soluble compounds. They pro- − year 1 over the period 1997–2006 (van der Werf et al. posed that, despite long-term sequestration of charcoal-C, 2009). Specifically, wildfires considerably alter forest char- it could be partially offset by stimulating the loss of plant acteristics through their impact on both trees and soil. litter-C. However, after a much shorter period – 240 days Despite emitting huge quantities of CO2 to the atmosphere, – Abiven and Andreoli (2011) reported no impact of these fires also produce large amounts of ash and char- charcoal on decomposition rates of different organic sub- coal which modify the characteristics of the forest lands. stances obtained from a mixed forest in Switzerland, which Actually, wildfires provide important information about the had been combined with the upper mineral horizon of a impact of charcoal on forest ecosystems (Table 1). Due cambisol. Therefore, it seems that the impact of charcoal to the lack of studies on the topic of biochar in forestry on C dynamics of surrounding organic substances depends systems, information of this type is crucial to increase on their nature, the soil conditions, and temporal duration. the understanding of related processes. For example, in Deforestation increases the impact of climate change the northern boreal zone of Sweden, a greenhouse study on the remaining forests. Global warming puts tropi- that encompassed wildfire-produced charcoal mixed with cal forests at risk of more frequent and severe droughts three different substrates obtained from diverse microhab- (Gullison et al. 2007). If the Amazon droughts of the last itats, revealed increased shoot-to-root ratio by Silver birch decade continue into the future, ∼55% of (Betula pendula Roth) and Scots pine (Pinus sylvestris L.). forests will be damaged, emitting between 15 and 26 Pg C This effect was attributed to the greater uptake of N and into the atmosphere (Nepstad et al. 2008). Modeling sug- other nutrients by trees that were presumably affected by gests that the accumulation of greenhouse gases (GHGs), the smaller binding of nutrients in the tree-litter phenolics and the associated increase in radiative forcing of the atmo- in the presence of charcoal (Wardle et al. 1998). This is sphere, will cause a decrease of more than 20% in rainfall in accord with DeLuca et al. (2006), who reported that across some parts of the Amazon Basin by the end of the wildfire-produced charcoal (1%) mixed with ammonium twenty-first century (IPCC 2008). (NH4: 99%), increased nitrification rates and decreased solution concentrations of phenolics in Ponderosa pine (Pinus ponderosa Doug. ex. ) litter. This is also in Afforestation of degraded lands

Downloaded by [University of Wyoming Libraries] at 12:33 05 October 2013 agreement with MacKenzie and DeLuca (2006) whose Land degradation is widespread, encompassing ∼24% of research in the same geographical region demonstrated the world’s terrestrial area, inhabited by about 1.5 bil- that wildfire produced charcoal was highly effective in lion people (Bai et al. 2008). Among the many effects sorbing litter-phenols of the understory elk sedge (Carex of these degradation processes on croplands and grazing geyeri Boott) and ericaceous kinnikinnick (Arctostaphylos lands, is the reduction in vegetation cover and depletion of uva-ursi (L.) Spreng.). They also reported that charcoal SOC, resulting in decreased formation and stability of the increased net nitrification in the ericaceous litter, but not soil structure (Lal 2002). A combined effect of these pro- in the sedge litter. cesses includes increased raindrop impact on the exposed The long-term residence time of ash, charcoal, or black surface, decreased hydraulic conductivity of the soil, and C has been widely acknowledged (Lehmann et al. 2008; enhanced loss of the fertile top layer by erosional pro- Abiven and Andreoli 2011; de Lafontaine and Asselin cesses (Stavi & Lal 2011a). The SOC lost through these 2011). Nocentini et al. (2010) discovered that the decom- erosional processes could be oxidized and emitted as CO2 posability of charcoal is dominated by the size of its to the atmosphere (Stavi & Lal 2011b), or buried and particles. In a study conducted in an Italian pine coastal accumulated in depositional sites (Gregorich et al. 1998). forest, they found that in charcoal produced by a moderate- Regardless, the depletion of SOC from the surface layer intensity wildfire, the charcoal fraction of <0.5 mm, further degrades the soil’s fertility and productive capacity accounted for 24% of the total charcoal mass, was rich in (Stavi & Lal 2011a). International Journal of Sustainable Development & World Ecology 169 DeLuca (2006) (2011) Wardle et al. (1998) DeLuca et al. (2006) MacKenzie and Wardle et al. (2008) Ball et al. (2010) Abiven and Andreoli Makoto et al. (2011) decreased 4 NH Silver birch, no impact on net growth of Scots pine; in some instances, increased shoot-to-root ratio of both species solution concentrations of plant phenolics germination and growth of Scots pine, but not that of Gmelin larch Charcoal mixed with Greater growth of − − − − Charcoal increased w) / litter Impact on trees Reference 99% w / 4 increased rate of nitrification in soil microbial biomass in some instances, and affected litter decomposition (1% NH humus increased mass loss of humus through either respiration or leaching of soluble compounds sorbing of litter-phenols, and augmented litter nitrification mineral soil augmented abundance of ammonia-oxidizing bacteria, and increased nitrification rates different organic materials in mineral soil did not increase decomposition rate of litter the soil’s pH, water content, and available P Impact on soil and Charcoal stimulated Charcoal increased Charcoal mixed in Charcoal increased Larix ) ), Scots Pseudotsuga pine Douglas-fir ( menziesii Douglas-fir gmelinii pine Downloaded by [University of Wyoming Libraries] at 12:33 05 October 2013 Table 1. Impact of wildfire-produced charcoal on soil and trees inLocation forest lands. Northern Sweden Cold Climate Various Soil type Silver birch, Scots Tree species Montana, USA Temperate Typic Dystrocryepts Ponderosa pine Charcoal mixed with Montana, USA Temperate Lithic Dystrustept Ponderosa pine, Northern Sweden Cold Not specified Scots pine Charcoal mixed with Idaho, USA Temperate Not specified Ponderosa pine, Switzerland TemperateEastern Cambisol Cold Brown taiga Various Gmelin larch ( Charcoal mixed with Victoria, Australia Temperate Not specified Various Not tested Not tested Santín et al. (2012) 170 I. Stavi

Wherever prevailing terrestrial and climatic conditions biochar could be applied throughout the project’s area. allow, degraded lands can be converted to afforestation In the cases of already established afforestation projects, projects. This could be relevant for most of the globe’s biochar could be applied only in the trees’ inter-rows. biomes. Also, afforestation of degraded lands could Furthermore, when calculating the biochar application improve ecosystem services and enhance rate of either new or already established afforestation conservation (Chazdon 2008). At present, afforestation projects, the terrain’s surface conditions should be taken projects take place in many countries and across several cli- into account as they considerably impact the accessible matic regions. Millions of smallholder farmers throughout land area. For example, steep terrains may impose difficul- the world are already engaged in and forest ties in either manual or mechanized application of biochar. management to compensate for the loss of access to woody Another example is exposed bedrocks, or bedrocks in very material and the degradation of natural forests (Boyd et al. shallow depths, that restrict the application of biochar in 2005). In his essay on of degraded lands, soil. Chazdon (2008) stressed that new forests will require adap- Whether conducted for co-production of bio-energy tive management as resilient systems that can withstand and biochar, or solely for the production of biochar, stresses of climate change, , and other the pyrolysis feedstocks could be diverse. Similarly to disturbances. other bio-energy sectors, feedstocks could include a range Several studies have revealed the capability of biochar of agricultural and organic materials, such as forestry application to restore degraded lands (e.g., Sohi et al. residues, domestic wastes, sewage sludge, and excess live- 2009; Stavi 2012). It is proposed that some of the biochar- stock manure. Also, designated highly productive agricul- amended degraded lands could be used for afforestation. tural crops that neither require high inputs nor compete Since biochar augments the retention of water and nutrients with food crops could be used as feedstocks (Tilman et al. in the uppermost soil layer and increases their availabil- 2009). At the same time, residues of agricultural crops, ity for plant uptake (Lehmann 2007), trees planted in the such as wheat straw or corn stalk, must not be considered biochar-amended lands are expected to experience favor- as relevant feedstocks. This is because the on-site reten- able conditions, which would foster their productivity. tion of such residues is crucial for maintaining the SOC Also, the alkaline nature of the biochar is expected to stock, supporting the soil food web, and protecting the soil alter the soil pH. This may be advantageous in highly surface from erosional processes (Lal & Pimentel 2009). weathered soils, where biochar may neutralize their acid- Established afforestation systems require permanent ity (Lehmann & Rondon 2006). Therefore, it is anticipated supervision and occasional maintenance actions such as that the increased productivity of trees will augment the trimming and . Wherever possible, some of the land’s restoration capacity. prunings should be left on the surface, aimed at prevent- The method of biochar application could be through ing the emergence of erosional processes, and replenishing spreading throughout the land surface, and then either the SOC stock (Jones et al. 2008). Under certain condi- incorporating into the soil, or retaining it on the ground. tions, the waste materials are completely cleared from the However, while retention of biochar on the intact ground afforested land in order to reduce the risk of fire outbreaks surface prevents the disturbance of the uppermost soil (Leinonen 2004). One way or another, some of the waste layer and therefore minimizes the risk of , it material could be used as feedstock for either bio-energy also decreases the potential improvement of soil nutri- or biochar production. Ogawa et al. (2006) proposed that ent status. Also, the light-weight biochar retained on in addition to its environmental advantages, the practice of the surface may be susceptible to redistribution over the biochar management could also have social and economic surface through wind or water force. Therefore, wher- benefits through the establishment of new businesses, new

Downloaded by [University of Wyoming Libraries] at 12:33 05 October 2013 ever possible, biochar should be incorporated into the job opportunities, and raised income of inhabitants in rural soil. Several types of machinery can be used to spread regions. Yet, economic calculations and life-cycle assess- biochar on the ground surface. Yet, so far, only few ments should be conducted on a site-specific basis in order spreaders have been developed specifically for biochar (or to ensure net economic profit and net C sequestration after wood ash) (e.g., Cox 2012; http://www.eng.askungenvital. the deduction of costs and emissions pertaining to waste se/machines.htm). Until such spreaders become more collection from the forest floor, transportation to the pyrol- widespread, biochar spread over extensive lands could ysis plant, and processing into end products. Providing be conducted through modified conventional spread- specific and effective environmental policies, some of the ers traditionally used to spread compost, manure, or costs could be covered by the inclusion of this management sludges. Small-scale application of biochar into the soil practice under the international C finance mechanism. This matrix could take place by using hand-operated rotavator option is further elaborated in the section ‘Regulations and machines. Applications over extensive land areas could be funding’. carried out with tractor-drawn ploughs, disk ploughs, or rotavators. In these cases, the application depth would be determined in accordance with the terrestrial conditions Reforestation projects and tree species. In a comprehensive research project, Niles et al. (2002) Ideally, the application of biochar should take place studied the potential C mitigation capacity of reforestation before the trees are planted. On these occasions, the projects across 48 sub-tropical and tropical developing International Journal of Sustainable Development & World Ecology 171

countries during a 10-year period between 2003 and 2012. lowest edge could be then used as feedstock for producing They calculated a reforestation rate of ∼1.7, 1.1, and bio-energy or biochar. For instance, if the residue rate is 0.7 million ha year−1 in Latin America, Asia, and Africa, ∼80 Mg ha−1 (see Gregg & Smith 2010) then the harvested respectively, potentially yielding a total of ∼3.5 million residues could reach up to ∼60 Mg ha−1. Considering that ha year−1. The corresponding potential vegetative-C accu- the conversion rate of vegetative material to biochar in slow mulation capacity, excluding the SOC, was calculated as pyrolysis – the thermal decomposition of biomass by slow ∼178, 96, and 42 Tg, yielding a total of ∼316 Tg over heating at low to medium temperatures (450–650◦C) – is the 10-year period. The C stocks of such systems could ∼35% (Sohi et al. 2009), then this amount could yield be increased considerably if biochar is applied to their ∼20 Mg biochar ha−1. Another widespread practice in soil. Similar to afforestation systems, biochar can be pro- some of the temperate and cold regions, including exten- duced on its own or as a by-product of the pyrolysis sive areas in Finland and the northern USA, process for production of bio-energy. It is possible that is the ‘whole tree method’, where the entire above-ground in developed countries, where related infrastructures are biomass is being used for either logging or the bio-energy well established, this track would be more feasible as a industries, and no residues are left on the ground surface complementary sector to the bio-energy industry. At the (Leinonen 2004). Considering the heavy environmental same time, in developing countries lacking such advanced cost of this practice, including the rapid diminishment of industries, the production of biochar would be probably SOC stocks and the increased risk of soil erosion, it seems introduced more easily if conducted through low invest- that rather than utilizing the residues exclusively for direct ments in technologies that produce only biochar. Either production of bio-energy, some of them could be converted way, addressing forest residues as a relevant feedstock to biochar. It is expected that on-site application of the pro- for bio-energy and biochar production, and utilizing the duced biochar in the deforested lands would considerably biochar as soil amendment in reforestation projects, could restore the quality of their soil and improve their restora- be perceived as a sustainable alternative to the intentional tion capacity, facilitating the establishment of reforestation burning of them. Yet, it is recognized that among many projects. Yet, even if some of the C is returned to the rural populations in developing countries, where fuelwood soil through biochar application, the ‘whole tree method’ and home-made charcoal encompass the main source of is highly un-recommended due to the increased risk of energy for domestic needs (Mead 2005), little motivation, accelerated erosion. if any, would be directed at using the charcoal (biochar) as In spite of the apparent benefits of biochar application soil amendment. Therefore, in order to induce the desired in forest lands, very little attention has been paid to this change in motivation, international policies should reg- management practice so far. For example, In Indonesia, ulate the practice of biochar application in forest soil Ogawa et al. (2006) noted that excess wood bark of Acacia as eligible for funding under the C finance mechanism. mangium stands could be used for biochar production, It is expected that in conjunction with extension activities which would be utilized for several purposes, such as fuel, aimed at educating local populations about its long-term water purification methods, and soil amendment in crop- advantages, this management practice could be extensively lands and forest lands. In another recent synthesis study, implemented. Ogawa and Okimori (2010) reviewed earlier studies of Also, it is acknowledged that even if the pyroly- biochar application in the Japanese forestry sector. They sis process for bio-energy production, coupled with the showed that bark-biochar powder combined with 0.1–1.0% use of biochar as soil amendment, could be considered of various chemical fertilizers, increased growth of both C-neutral, or under optimistic conditions as C-negative shoot and root of Pinus thunbergii. In addition, this treat- (Lehmann 2007), the related procedures of feedstock col- ment increased yields of the associated edible mycorrhizal

Downloaded by [University of Wyoming Libraries] at 12:33 05 October 2013 lection, transportation, processing, and spreading would fungus Rhizopogon rubescens. Moreover, they showed that require utilization of fossil fuel, emitting large amounts the application of biochar combined with chemical phos- of GHGs. Therefore, life cycle assessments of the con- phate (P) and different mycorrhizal fungi augmented the version of residues into bio-energy or biochar should be survival rate of seedlings from several pine species. In a conducted on a site-specific basis, aimed at verifying the greenhouse study, Bell and Worrall (2011) examined the environmental sustainability of this management practice. impact of biochar on a humified organic soil obtained from In order to be considered pertinent, the overall environmen- a British temperate forest. The biochar was applied at rates tal footprint of this management practice should be lower of 6.25, 62.5, and 87.5 Mg ha−1, and compared to control, than that under the alternatives (e.g., intentional burning or non-amended soil. They reported that biochar treatments any other treatment of residues). had no effect on net ecosystem respiration or on nitrate In managed and planned reforestation lands, it is (NO3) flux and dissolved organic C (DOC) concentration preferable that some of the residues would be retained on in the soil leachate. However, soil pH was reported to the forest floor in order to maintain the SOC stock and respond positively to the biochar rate. control erosional processes (Jones et al. 2008). In their Despite scant reporting on the utilization of biochar in review of the potential production of bio-energy from for- forest lands, the use of wood ash derived from biomass est wastes, Gregg and Smith (2010) stressed that retention burning in power plants has been intensively studied of forest residue should encompass at least 20 Mg ha−1. (Table 2). Specifically, utilizing wood ash as soil amend- Using this limitation, any amount of residues beyond that ment in forestry systems offers a means to counteract soil 172 I. Stavi (Continued) et al. (2006) (2008) et al. (2004) et al. (2006) Saarsalmi Augusto et al. Saarsalmi Solla-Gullón than aggregated ash; low rather than high rate doses; for adult rather than young stands; in acidic rather than alkline soils pelleted or granulated ash, rather than loose ash at rates adapted to the liming needs of soil Loose rather Utilizing − Ash application Reported N is the most limiting nutrient for tree growth, decreasing biochar impact with mineral NonsoilN concentra- tion; increased Cd concentration in soil; too high pH under certain conditions, negatively impacting understory vegetation with mineral NonsoilN liming and fertilizing capacity of the ash impediments Recommendation Reference In mineral soils, No effect of ash No effect of ash Moderate with 1 − , Ca, and Mg in and trees 4 the short-term, and increased soil pH in the long term; almost no impact on trees in mineral soils, and a positive impact on trees in organic soils concentrations and higher pH in soil; increase in needle nutrient concentrations; slight increase in tree growth after 5 years and no increase after 10 years concentrations and higher pH in soil; positive impact on tree growth only for the biochar rates of 2.5 or 5Mgha mineral N available Ca, Mg, and K; increased foliar K, Ca, N, and P concentrations, and greater tree height, diameter, and biomass SO Impact of ash on soil Increased nutrient Increased nutrient Increased soil pH and 1 − Ntoa + + ( ( ) ) rate 1 1 1 1 − − − − 185 kg N ha ash, 3 Mg ha rate of 120–150 kg ha and peat ash to rates of 1, 2.5, and 5 Mg ha ash,10 and 20 Mg ha Ash source and Loose wood Wood-, bark-, Wood-bark tree species 75-year-old stands of Norway spruce and Scots pine Scots pine stand Douglas-fir stand Stand age and 5-year-old Downloaded by [University of Wyoming Libraries] at 12:33 05 October 2013 Umbrisol Cold Haplic Podzol 31 to Temperate Humic Cold Haplic podzol 60-year-old Cold Various (review) Various (review) Various (review) Increased soil K, Na, Finland Spain Finland countries Table 2. Reforestation lands amended with wood ash derived from biomassLocation burning in power plants. Southern Climate Soil type Northern Northern Nordic International Journal of Sustainable Development & World Ecology 173 et al. (2010) et al. (2009) (2011) et al. (2008) Saarsalmi Helmisaari Santalla et al. Solla-Gullón combined with P fertilizer ash, comprised of fly ash and bottom wood ash is better than sole fly ash as it prevents the release of elements to soil water and reduces the risk of heavy metal con- tamination − Biochar Mixed wood Reported concentration in soil availability; decreased N availability impediments Recommendation Reference Increased Cd −− − Decreased P and trees concentrations and higher pH in soil; smaller fine root growth but greater overall tree growth; slight increase in tree growth concentrations and higher pH in soil; overall increased microbial activity and slight increase in Norway spruce growth but no effect on Scots pine and availability of P, C a ,during M g 5 , years after a n dapplication; K positive effect of ash on tree height and diameter after 5 years availability and greater tree growth when applied with P fertilizer Impact of ash on soil Increased nutrient Increased nutrient Increased soil pH, Increased nutrient + + ( ( 1 1 − − ) ) rate 1 1 1 1 − − − − 150 kg N ha 150 kg N ha wood-bark ash of Monterey pine and Pinus pinaster (Maritime pine Aiton), 5 and 10 Mg ha ash, 7.5 Mg ha bark ash, 3Mgha bark ash, 3Mgha Ash source and Mixed Mixed wood Wood burnt- Wood burnt- tree species stand. The study initiated on stand establishment and continued for 5 years Monterey pine stand stand of Scots pine and 45-year-old stand of Norway spruce Norway spruce stand Stand age and 31-year-old Downloaded by [University of Wyoming Libraries] at 12:33 05 October 2013 Umbrisol Temperate Umbric regosol Monterey pine Sub-humid Alumi-humic Cold Haplic podzol 31-year-old Cold Haplic podzol 45-year-old Spain Spain Finland Finland Table 2. Continued. LocationNorthern Climate Soil type North-west Southern Southern 174 I. Stavi

acidification and to compensate for nutrient loss result- period, ash mixed with mineral N reduced the biomass of ing from intensive logging practices, such as whole-tree fine roots to ∼30% less than that under soil not amended harvesting (Saarsalmi et al. 2004). For example, in north- with either ash or mineral N. At the same time, this treat- western Spain, Santalla et al. (2011) examined the impact ment increased K concentrations in needles, but overall of mixed wood ash, applied at a rate of 7.5 Mg ha−1,on tree growth was similar between this treatment and the the soil nutrient status of an intensive forest system planted non-amended soil. In a study in 31- and 75-year-old conif- with Monterey pine (Pinus radiata D. Don). In this sub- erous stands in southern Finland, Saarsalmi et al. (2004) humid Mediterranean region, the A horizon of the soil is reported that wood ash alone had no effect on the P, K, and rich in organic matter, highly acidic, and with low avail- Ca concentrations in the needles, but ash combined with able nutrients, including P,calcium (Ca), magnesium (Mg), N fertilizer increased concentrations of these nutrients in and potassium (K). Santalla and colleagues demonstrated the needle. Overall, they reported no impact on tree growth that the application of ash restored soil reserves of Ca, Mg, under ash alone, when compared with a slight increase in and K in the soil’s organic layer. This is in accord with tree growth under ash combined with N. That slight impact Saarsalmi et al. (2004), who noted that the forest humus appeared during the first 5 years after application and then layer acts as a trap for many of the elements added in diminished. However, Saarsalmi et al. (2006) reported a wood ash, resulting in a long-lasting, nutritional effect of positive impact of biochar combined with mineral N on the ash in the soil. Yet, Santalla et al. (2011) also stated growth of Scots pines even 23 years after the application. that the application of wood ash decreased the availabil- Above all, the key determinants of wood ash chem- ity of P. They attributed this effect to the charcoal content istry are the tree species combusted, the nature of the of ash, which temporarily reduced the solubility of min- burning process, and the prevailing conditions at the appli- eral P. They added that this effect could have a specifically cation site. For example, wood ash from hardwood species adverse impact on acidic soils in temperate forests, where contains higher levels of macronutrients in their ash than P is the most limiting factor. They also reported that the conifers, and their silica (SiO2) content is usually lower. application of wood ash combined with mineral P fertilizer With regard to the conditions of burning, a furnace tem- at rates of 7.5 Mg ash ha−1 and 65 kg P ha−1, increased perature of between 500◦C and 900◦C is critical for the P concentration in needles, litterfall, and soil. In addition, retention of nutrients, particularly K. This temperature also Santalla and colleagues indicated that wood ash decreased determines the concentrations of potentially toxic compo- soil N mineralization rate and mineral N concentrations. nents in the ash (Pitman 2006). Also, the mode of ash They attributed this effect to the greater microbial activity application seems to have a considerable impact on nutrient in response to the better nutrient availability, along with the availability for trees. For example, solubilization of wood- effect of the very high C : N ratio in the ash. They noted bark ash could be low when spread on the ground surface that despite not limiting primary productivity under the without being incorporated into the soil (Solla-Gullón et al. studied conditions, this impact may adversely affect tree 2006). Conversely, incorporation into the soil was reported growth where decreased N availability could induce N defi- to increase solubility of wood ash compounds, augmenting ciency in plants. This effect is supported by other studies soil fertility and increasing tree growth (Solla-Gullón et al. (Augusto et al. 2008; Saarsalmi et al. 2010) which demon- 2008). In addition, the size of ash particles is also expected strated that in mineral soils and in infertile sites, growth is to play a role in impacting soil features. For instance, loose mainly dependent on N availability. Saarsalmi et al. (2004) ash material was reported to have greater reactivity than commented that since on poor mineral soils the growth pelleted or granulated ash (Saarsalmi et al. 2004), acceler- response to wood ash alone seems to be insignificant or ating the rate of release of Ca, K, and Na (Pitman 2006). even declined, the direct economic benefit of this man- Therefore, ashes of certain particle size and specific sur-

Downloaded by [University of Wyoming Libraries] at 12:33 05 October 2013 agement practice is negligible. Conversely, Solla-Gullón face area could assist in mitigating undesired high acidity et al. (2008) showed that ash application in N-rich min- of soils. eral soils of temperate areas significantly improved tree Additionally, one of the major concerns regarding growth. wood ash is that it might increase concentrations of heavy The impact of wood ash combined with mineral N on metals in soil. For example, the application of wood ash plant nutrient availability and tree growth has been inten- was reported to increase cadmium (Cd) concentration in sively studied. For example, in southern Finland, 3 Mg the soil’s organic layer in several forests (e.g., Saarsalmi ha−1 of wood burnt-bark ash combined with 150 kg N et al. 2004). In this regard, Pitman (2006) commented that ha−1 applied in the soil of a 45-year-old Norway spruce fly ash – the lightest component that accumulates in the flue (Picea abies (L.) Karst.) was reported to increase pH, system – can contain high concentrations of heavy met- base saturation, and total and extractable concentrations of als such as Cd, copper (Cu), chromium (Cr), lead (Pb), nutrients including P, K, Mg, and Ca in the soil’s organic and arsenic (As) and that this ash should not be used as layer (Helmisaari et al. 2009). Similar effect was reported soil amendment. However, Solla-Gullón et al. (2008) noted by Saarsalmi et al. (2010) who studied, in the same geo- that mixed wood ash, comprised of fine fly ash, and bottom graphic region, the impact of burnt-bark ash combined wood ash is much less reactive and contains lower amounts with mineral N in a 31-year-old Scots pine stand. However, of trace elements than fly wood ash alone, reducing the risk Helmisaari et al. (2009) reported that during a 10-year of heavy metal contamination. Finally, it is yet questionable International Journal of Sustainable Development & World Ecology 175

whether higher application rates of wood ash augment the agroforestry (Zomer et al. 2009). This land use is a multi- potential productivity of forestry systems (Saarsalmi et al. purpose practice and, according to the landowner objec- 2006), or increase the risk of toxic effects (Pitman 2006). tives, can involve any combination of timber, row crop, In this regard, it is important to stress that, depending on pasture and forage, fruit crop, fuelwood, wildlife habitat, feedstock origin and pyrolysis conditions, biochars may or recreational sites (Workman & Allen 2004). Specific also contain heavy metals, as well as other contaminants. agroforestry practices include alley cropping, multi-storey However, the ecotoxic effects of these contaminants can cropping, or silvopastoral systems, where trees or shrubs be avoided by testing the feedstocks before pyrolyis and are intercropped with grain crops, vegetables, or forages examining the biochars before they are applied to soil (Kandji et al. 2006). The trees themselves can be multi- (Ernsting 2011). Yet, there is great need to further assess purpose, for example, providing fruits, producing small- these mechanisms, as well as identify specific feedstock diameter wood for construction, supplying fuelwood or characteristics and operational conditions which lead to the stakes (Boyd et al. 2005), or be used for hedging, shade, formation and retention of these contaminants in the final ornamentals, or medicinal plants (Maroyi 2009). The mul- biochar product (Verheijen et al. 2010). tiple products of an agroforestry system are available at The cost of converting forest residues into bio-energy different time intervals, can utilize space more effectively, or biochar varies greatly and depends on a wide range and extract nutrients from different soil layers more effi- of variables. These include the terrain’s features, climate ciently. The diversity of products help farmers to cope with conditions, fuel price, utilized technology for harvesting, crop failure (Workman & Allen 2004) and can raise house- collection and processing of feedstocks, the use of trans- hold incomes (Maroyi 2009). Such systems in the humid portation means, and distance to the power plants. Since tropics are part of a continuum of landscapes ranging a major economic constraint lies in the costs associated from primary and managed forests to croplands and grass- with transportation (Leinonen 2004), the conversion of lands (Kandji et al. 2006). Overall, agroforestry systems residues into bio-energy and biochar is best conducted on- were reported as being capable of sequestering between site. Therefore, the construction of pyrolysis plants for 15 and 228 Mg C ha−1 (Kandji et al. 2006). Average C bio-energy production, or merely kilns for production of storage by agroforestry systems has been estimated by biochar, should be conducted as close as possible to the Montagnini and Nair (2004) as 9, 21, 50, and 63 Mg reforested lands (Matovic 2011). Either way, economic Cha−1 in semi-arid, sub-humid, humid, and temperate calculations for the production of bio-energy or biochar regions, respectively. For smallholder agroforestry systems should be implemented on a site-specific basis and encom- in the tropics, potential C sequestration rates range between pass all costs related to the processing of feedstocks. 1.5 and 3.5 Mg C ha−1 yr−1. Nevertheless, they stressed Similar to afforestation projects, also in reforestation lands that while agroforestry systems with perennial crops may the application of biochar should ideally be conducted be efficient C sinks, intensively managed agroforestry sys- before planting the trees, augmenting the biochar applica- tems with annual crops are more similar to conventional tion capacity of the land unit, and increasing the system’s agricultural lands in terms of net C fluxes. Moreover, they potential production capacity. Also, similar to afforested added that even the perennial crop-tree combinations do lands, physical restrictions in the terrain’s surface should not attain C sequestration capacities comparable to natural be considered when calculating the biochar application forests. capacity. Agroforestry systems not only provide a great opportu- Overall, it seems that the impact of wood ash on soil nity for sequestering C, and hence help mitigate climate characteristics and stand productivity are site-dependent, change, but they also enhance the resilience of agricul- vary greatly on the temporal axis, and are affected by the tural systems and increase additional ecosystem services.

Downloaded by [University of Wyoming Libraries] at 12:33 05 October 2013 ash features. On the whole, to date, most of the studies Such systems can efficiently enlarge water use efficiency, which have examined the impact of wood ash in forestry provide shading, increase nutrient turnover, and improve systems were implemented under humid and temperate- micro-habitat conditions for agricultural crops, increasing to-cold regions, on acidic soils, and for coniferous stands. their adaptation capacity to climatic changes. Moreover, At the same time, research under Mediterranean or drier Kandji et al. (2006) showed that in the event of leguminous and hotter regions, on alkaline soils, and for broadleaf trees, agroforestry systems can provide N to crops, reduc- stands is extremely scarce. ing input on fertilizers. However, such trees may increase emissions of nitrous oxide (N2O) compared with unfertil- ized systems. Yet, it is expected that N-fertilizer amended Multi-purpose agroforestry soils emit N2O to at least the same extent as legume tree- Agroforestry systems – agricultural lands with more than based agroforestry systems. In addition, compared with 10% tree cover – occur on 46% of global agricultural mono-species croplands, agroforestry systems may have land area, and affect 30% of the world’s rural population. better resilience to pest infestation. As shown by Paul et al. Therefore, this land use represents over 1 billion ha of (2010), increased plant biodiversity due to mixing trees land and 558 million people worldwide and is particularly and herbaceous species in agricultural landscapes, results prevalent in , Central America, and South in positive interactions that assist in controlling outbreaks America, with over 80% of agricultural land area under of pests and diseases. As stressed by Stavi & Lal (2013), 176 I. Stavi

an additional provided by agroforestry All the relevant feedstocks for other tree-based agro- systems is the better erosion control, sustaining the on-site ecosystems could also be pertinent for fruit tree orchards quality of soil and off-site quality of water sources. and bio-energy plantations. In addition, prunings from Relevant feedstocks for biochar production in the orchards and plantations could also supply con- agroforestry systems could be the tree prunings. siderable amounts of feedstocks. For example, in the Nevertheless, it is expected that emissions of GHGs Veneto region of northern Italy, vines (Vitis spp.), olive associated with the collection of prunings, transportation trees (Olea europaea L.), apple trees (Malus domestica to the pyrolysis plant, and processing would decrease net borkh.), pear trees (Pyrus spp.), peach trees (Prunus per- amounts of C sequestration. Yet, it should be acknowl- sica (L.) Batsch), citrus trees (Citrus spp.), almond trees edged that some practices (e.g., taking the prunings out of (Prunus dulcis (Mill.) D.A. Webb), and hazelnut trees the field) will be carried out in either case and, therefore, (Corylus spp.) were reported, respectively, to produce have to be deducted from the biochar-track’s life cycle 2.53–2.90, 1.70–2.00, 0.15–2.40, 0.09–2.00, 0.20–2.90, assessments. Moreover, since many farmers routinely 0.32–1.80, 0.15–1.70, and 0.19–2.80 Mg prunings ha−1 burn prunings in order to dispose them, the conversion year−1 (Santacroce 2010). In sub-tropical Asia, coconut to biochar could be considered highly sustainable. In the trees and cocoa trees were reported, respectively, to pro- cases of mixed farms that include land cultivation and duce 5–10 and ∼25 Mg residues ha−1 year−1 (Koopmans livestock raising, the excess livestock manure could also & Koppejan 1997). In the Middle East, date palm orchards be used for this purpose. However, residues from the produce ∼7.5 Mg dry fronds ha−1 year−1 (personal com- main (inter-tree) crops must not be considered as viable munications, Stavi). Similar to agroforestry systems, also feedstocks because of their important role in preserving in fruit tree orchards and bio-energy plantations, emissions the quality and productive capacity of the soil in the of GHGs are expected during collection, transportation, inter-row spaces. and processing of the prunings. Yet, as with agroforestry It is expected that the application of biochar in the systems, the collection of prunings is inevitable in the soil of agroforestry systems would decrease leaching of maintenance of many of the orchards and plantations. nutrients, reducing contamination of below-ground water Specifically, for the date palm orchards, where many farm- sources. Also, the increased stability of the surface soil ers burn the fronds in order to dispose them (personal com- would reduce the generation of water overland flow and munications, Stavi), their conversion to biochar impose net decrease frequency and magnitude of erosional processes. environmental profit. Tree plantations for bio-energy crop- These effects are expected to lessen eutrophication of ping produce smaller, similar, or greater amounts of feed- above-ground water sources and reduce siltation in reser- stock. For instance, across the USA, poplar (Populus spp.) voirs. The application of biochar was also reported to and willow (Salix spp.) are extensively cropped for bio- decrease emissions of N2O and methane (CH4)fromsoil energy, producing, respectively, between 1.44–1.88 and (Rondon et al. 2005). The expected increased fertilizer 1.82–1.98 Mg of dry biomass ha−1 year−1 (DeLaTorre efficiency in the biochar-amended soil (Lehmann 2007) Ugarte et al. 2003). In the sub-Mediterranean region of would enable lowered fertilizer rates, decreased produc- Spain, 3-year harvest rotations of eucalyptus (Eucalyptus tion costs, and reduced off-site and on-site emissions of spp.) were reported to produce much greater yields of GHGs. A recent study by Stavi & Lal (2013) highlighted between 45 and 60 Mg dry biomass ha−1 at the third and the high capacity of the practices of agroforestry systems sixth years after planting (Tolosana et al. 2010). and biochar application in croplands – as opposed to other Similar to other sources of feedstocks, assuming a con- agricultural practices – in offsetting climate change. It is version rate from biomass to biochar of ∼1:3 (Sohi et al. hereby suggested that the combination of these two prac- 2009) and considering the application of the minimal rec- −1 Downloaded by [University of Wyoming Libraries] at 12:33 05 October 2013 tices in the same land unit would link their climate change ommended rate of 10 Mg ha (Chan et al. 2007), highly mitigation and adaptation capacities, further increasing productive bio-energy crops, such as eucalyptus, could their agricultural and environmental benefits. easily provide a sufficient amount of biochar for on-site application during a single harvest. Using the same cal- culations, the on-site utilization of biochar produced from Mono-culture of fruit tree orchards and bio-energy other bio-energy crops and fruit tree prunings could be plantations conducted gradually along the temporal axis. Otherwise, Similar to afforestation, reforestation, and agroforestry biochar application in the soil of these crops could rely on systems, the application of biochar in soil could also be off-site sources. a relevant management practice in mono-culture fruit tree Early evidence of biochar (then called charcoal) use as orchards and bio-energy tree plantations. Also, similar to a soil amendment in fruit trees was indicated for Satsuma other tree-based agro-ecosystems, the biochar would be mandarin (Citrus unshin Marc.) trees on trifoliate orange preferably applied to the whole area before planting the (Poncirus trifoliate Raf.) rootstocks in Japan. Biochars pro- trees, maximizing C sequestration capacity, and augment- duced from rice husk, citrus juice sediments, or spruce ing the system’s resilience. In the event of already estab- bark were reported to increase root length, enlarge shoot lished orchards or plantations, biochar could be applied productivity, augment NPP, and stimulate development of only in the inter-row spaces. vesicular arbuscular mycorrhiza (Ishii & Kadoya 1994). International Journal of Sustainable Development & World Ecology 177

In addition to the impact on tree productivity, and similar to 48–147 Pg C in forestry lands by the end of the twenty-first agroforestry systems, the application of biochar in orchards century. and plantations is expected to decrease their environmental Following the 13th Conference of the Parties of the footprint by reducing fertilizer rates. It is anticipated that Framework Convention on Climate Change the outcome will be a reduction in direct and indirect emis- (UNFCCC [2007, ]), the parties were encouraged to sions of GHGs and lowered the levels of pollution in above- seek further innovative and efficient means to mitigate and below-ground water sources. climate change. One of the main mechanisms suggested was the Reducing Emissions from Deforestation and Degradation (REDD) of forest lands in developing coun- Regulations and funding tries, aimed at maintaining forest C stocks by slowing or The world’s focus on mitigating C emissions is pro- eliminating anthropogenic-induced disturbances (Seymour gressively increasing. Specifically, international projects and Forwand 2010). The UN-REDD program supports in developing countries are concentrating on the slowing countries to develop capacities for reducing emissions from of tropical deforestation and promotion of reforestation deforestation and forest degradation and to implement projects (Niles et al. 2002). An efficient economic mecha- future mechanisms in a post-2012 climate regime (Verchot nism – the C finance mechanism – allows countries to trade and Petkova 2010). This development has resulted in the in emissions, where developing countries sell C credits establishment of many public and private REDD initia- aimed at assisting developed countries to achieve emis- tives at local, national, and global levels. Nonetheless, to sion targets. Such mechanisms could potentially generate be effective, REDD efforts will not only have to reverse considerable funding for forestry projects in the develop- the economic incentives that drive forest loss but will also ing world (Miles & Kapos 2008). Yet, key requirements need to clarify , lead international endeavors in needed to curtail deforestation include strengthened tech- limiting illegal logging and trade, and manage trade-offs nical and institutional capacities in many developing coun- among competing needs (Seymour & Forwand 2010). The tries, agreement on a rigorous system for measuring and main factors determining the success of REDD projects monitoring emission reductions, and de facto commitment include: clearly formulated design; governance and land by developed countries to create demand for C credits tenure; equity and transparency; indigenous peoples’ rights (Gullison et al. 2007). Also, in many developing coun- and knowledge; local–international coordination; and local tries, one of the major challenges is to maintain a balance and institutional capacities (Dulal et al. 2012). Successful between meeting increased market demand for forest prod- implementation of REDD mechanisms would generate a ucts, alleviating poverty, and protecting natural resources. number of gains, including: (1) environmental benefits, These three conflicting needs are meant to be addressed by such as biodiversity protection, soil and water conserva- small-scale, offset projects under Article 12 of the Clean tion, and ecosystem restoration; (2) social benefits related Development Mechanism (CDM) of the Kyoto Protocol with sustainable development and poverty reduction; and (1998). The objective of this framework is to improve (3) governance benefits associated with improved protec- livelihood conditions in developing countries by providing tion of human rights (Verchot & Petkova 2010). a market mechanism aimed at mitigating climate change It is proposed that alongside decreases in deforesta- through sustainable use of natural resources (Boyd et al. tion rates and increases in reforestation and afforestation 2005), such as forestry systems. efforts, biochar management practice in forestry and tree- Yet, the CDM has very strict rules for participation that based agro-ecosystems ought to be considered as a legit- may be beyond the reach of small-scale farmers. There is a imate strategy for C sequestration. In this regard, it must need for institutional support at the national, regional, and be emphasized that the production of biochar – either

Downloaded by [University of Wyoming Libraries] at 12:33 05 October 2013 international levels to facilitate effective participation of on its own through low-tech stoves or to a much larger these farmers in forestry projects (Kandji et al. 2006). Also, extent as a by-product of the pyrolysis process for produc- to ensure the successful implementation of such projects, tion of bio-energy – requires investments in apparatus and the local social, cultural, and political context must be com- infrastructure. It is expected that, unless biochar is con- prehensively addressed. In addition, active participation sidered valuable merchandise, most landowners and users, in decision-making by local stakeholders and community- being either individuals, commercial companies, NGOs, based organizations, free access to information by the local or others, will not invest in its production and utilization. populations, and local ownership of different project com- As such, financing to facilitate the development of biochar ponents are crucial (Boyd et al. 2005). Moreover, CDM projects in forestry and tree-based agro-ecosystems must payments should be high enough to encourage individu- be regulated. It is therefore important to emphasize that als to implement forestry projects. For example, Conant the application of biochar in soil is not clearly eligi- (2011) showed that a price of $US 75 Mg−1 C would gener- ble for funding under the CDM (Whitman and Lehmann ate such motivation, whereas a lower price would serve as 2009). To address this, an inter-governmental interven- a disincentive for the initiation of such projects. Sohngen tion should adjust the C finance mechanism to explicitly and Sedjo (2006) calculated that prices ranging between include the biochar management practice aimed at aug- $US 100–800 Mg−1 C could lead to global sequestration of menting C sequestration in soil, while increasing vegetative 178 I. Stavi

productivity and reducing environmental footprint of land- Integration and conclusions use change. A progression such as this would enable a Natural sequestration of C in forestry and tree-based valuation of biochar application in forestry and tree-based agro-ecosystems occurs in a relatively efficient manner. agro-ecosystems according to the price given for offsetting Yet, the amounts of C sequestered in these systems are of CO2 emissions. smaller than in primary forests. Moreover, trees’ biomass- In a comprehensive life cycle assessment of pyrolysis C and organic-C in the soil of these systems are not of different feedstocks and the application of the biochars safely sequestered, and large parts of them sooner or later in croplands, Roberts et al. (2010) concluded that these decompose, emitting enormous quantities of CO2 to the systems’ viability is dependent on the costs of feedstock atmosphere. Applying biochar to the soil of such sys- production and pyrolysis process, as well as on the value of tems would considerably increase the non-decomposable C offsets. Roberts and colleagues calculated that in order fraction of C in their soil, augmenting their capacity to to be profitable, a minimum CO offset price would need 2 offset concentrations of atmospheric CO2. If considering −1 −1 to be $US 40 Mg forcornstover,$US62Mg for an application rate of between 10 and 100 Mg biochar −1 switchgrass, and only $US 2 Mg for yard waste. They ha−1 (similar to that in croplands: Chan et al. 2007), and demonstrated that livestock manure may also be promis- knowing that biochar-C concentration ranges between 50% ing for biochar production. As discussed above, forestry (Lehmann et al. 2006) and 78% (Gaskin et al. 2008), and waste and residues derived from fruit tree orchards and assuming that the decomposable portion of biochar-C is bio-energy plantations may also be viable as feedstocks for up to 20% (Ogawa et al. 2006), this management prac- biochar production. tice could sequester between 4 and 62 Mg biochar-C ha−1 It must be stressed that, unlike the CDM or REDD over the long run. In a recent synthesis study, lands suit- programs that have been applied exclusively for develop- able for afforestation and reforestation were reported to ing countries, the use of biochar in soils of forestry and encompass 24, 333, 195, 93, 63, and 41 million ha in tree-based agro-ecosystems should be regulated for the Central America, Southern America, sub-Saharan Africa, developed world as well. Further, it is suggested that as East Asia, South Asia, and Southeast Asia, respectively. long as regulations for biochar projects remain unresolved, Therefore, assuming a global cover of ∼750 million ha payments should be given by authorities to landowners to of these lands (Zomer et al. 2008), and an additional accomplish improvements in related ecosystem services. 1 billion ha of agroforestry systems (Zomer et al. 2009), The most relevant ecosystem services are C sequestration, the total relevant land area could comprise of 1.75 bil- soil erosion control, preservation of off-site water source lion ha. Applying biochar to these lands could poten- quality, and increased biodiversity. An additional environ- tially sequester up to a maximum of 109.2 Pg biochar-C mental benefit stems from the fact that the application (Figure 1). However, as emphasized above, the available of biochar in tree-based systems is expected to augment area may be smaller due to certain terrestrial conditions their wood and food product yields, lessening motivation such as steep slopes or rocky surfaces. Additionally, wher- for further deforestation. Extensive research is required ever forestry lands are subject to extreme, harsh terrestrial to investigate the potential of biochar application in soil conditions, it may be impossible to apply biochar mechan- of forestry and tree-based agro-ecosystems, with a goal ically. Under such conditions, manual application would of improving their climate change mitigation and adap- only be possible to the planting spots, where it would tation capacities. This should include field experiments merely be mixed with the soil to be filled in the planting under a range of geographical settings, as well as extrap- pits. Nevertheless, this limitation would presumably not olations and modeling studies on regional and global occur in agroforestry systems, where the trees’ inter-row scales. spaces – assumed to cover 50% of the ground surface – are Downloaded by [University of Wyoming Libraries] at 12:33 05 October 2013

Minimal track Maximal track –1 Biochar rate (Mg ha ) 10 100 Biochar-C concentration (%/100) 0.5 0.78 0.5 0.78

Recalcitrant biochar-C concentration (%/100) 0.8

Land area (billion ha) 1 1.75 1 1.75

Assumed accessible land area in already- 0.5 1 0.5 1 0.5 1 0.5 1 established agroforestry systems (%/100)

Biochar-C sequestration capacity (Pg) 2 4 5 10.92 20 40 50 109.2

Figure 1. Potential biochar-C sequestration capacity in afforestation, reforestation, and agroforestry systems around the world. Note: For clarity purposes, only 8 tracks are presented. The total number of possible tracks is 16, all of which lie in the range between 2 and 109.2 Pg. International Journal of Sustainable Development & World Ecology 179

typically cultivable. Therefore, if consider only the already Paper No. 71. Norwich: Tyndall Centre for Climate Change established agroforestry systems, the minimum biochar-C Research. sequestration capacity would be of 2 Pg. An additional con- Canadell JG, Raupach MR. 2008. Managing forests for climate change mitigation. Science. 320:1456–1457. doi:10.1126/ siderable amount could be sequestered in the soil of the science.1155458. world’s fruit tree orchards and bio-energy plantations. Chan KY, Van Zwieten L, Meszaros I, Downie A, Joseph S. 2007. The biochar management practice could improve soil Agronomic values of greenwaste biochar as a soil amend- quality, increasing the resilience of forestry and tree-based ment. Aust J Soil Res. 45:629–634. doi:10.1071/SR07109. agro-ecosystems and promoting their adaptation capac- Chazdon RL. 2008. Beyond deforestation: restoring forests and ecosystem services on degraded lands. Science. ity to the changing climatic conditions. 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