Environmental Effects and Carbon Sequestration Potential of Returning Agricultural Waste to Field By Carbonization

The utilization of agricultural waste as a resource is a key topic of research in various countries. Converting waste into biochar through carbonization is one of the main treatment methods. As the end product of biomass raw material resource utilization, biochar is produced by pyrolysis under anaerobic or anaerobic conditions and has high carbon content and large specific surface area.

In recent years, due to its excellent physical and chemical properties, biochar has been widely used in the field of returning to the field. Because of its high specific surface area and rich pore structure, it can effectively improve soil porosity, optimize soil structure, and improve soil water holding capacity [1-3]. Abundant elemental composition and surface functional groups can also introduce micronutrients needed for soil and plant growth [4,5], and retain nutrients. At the same time, returning biochar to the field can also sequester CO₂ in the form of Total Organic Carbon (TOC) and Soil Organic Carbon (SOC), showing obvious carbon sequestration and emission reduction potential [6,7].

Therefore, the carbonization of agricultural waste back to the field is a win-win option for soil improvement and carbon sequestration. In summary, this paper summarizes the current research on biomass carbonization technology and biochar returning to the field, summarizes the impact of biochar returning to the field on soil physical and chemical properties, and studies the carbon sequestration and emission reduction potential of biochar returning to the field. The application provides theoretical support (Figure 1).

Figure 1: Carbon fixation and emission reduction of agricultural waste carbonization.

Carbonization technology

Carbonization technology refers to the process of heating agricultural waste, forestry waste, sewage sludge and other biomass raw materials in a low-oxygen or anaerobic environment to decompose the molecules to form biochar, bio-oil and non-condensable gas products, the main purpose is to obtain solid product biochar [8]. At present, the main methods of biomass carbonization include a series of methods such as traditional pyrolysis carbonization, hydrothermal carbonization, and microwave carbonization. Traditional pyrolysis carbonization is widely used, which has the advantages of large output, high efficiency and simple operation. Most biochar products are produced by traditional pyrolysis carbonization methods [9].

In the process of biomass pyrolysis and carbonization, the pyrolysis temperature and reaction time are important indicators related to the yield, performance, and physical and chemical properties of biochar. Rapid Pyrolysis (500 °C), slow pyrolysis (400 °C) and gasification (800 °C) [10]. Among them, temperature is the decisive factor for the physical and chemical properties and structural characteristics of biochar. The change of temperature will make the biochar produced from the same biomass raw material have huge differences in physical and chemical properties. Under normal conditions, high temperature will cause higher specific surface area and Pore volume [11].

Biochar is mainly produced from waste biomass. In theory, all biomass can be used as raw material for biochar production. At present, the raw materials used to prepare biochar mainly include straw, fruit shell, poultry manure, wood chips, bagasse and sludge. Biochars prepared from different biomass raw materials have different physicochemical properties, especially the chemical properties of biochars, such as elemental composition, H/C ratio, C/N ratio, and ash content. For example, the ash content of biochar produced from wood raw materials is usually lower than other biochars [12]. The ash content determines the quality and economic benefits of biochar. Low ash content means higher economic benefits, which is also the current market. The reason why there are more wooden biochar products.

However, the combination of biomass raw materials and carbonization technique affects the properties of biochar. There is no conclusive evidence to establish the surface features and process parameters of biochar, and the physicochemical properties of biochar produced by various types of biomass carbonization employing various process parameters are quite varied. Consequently, carbonization technology has consistently been a hot topic in the domains of agriculture, the environment, and energy.

Physical and chemical characteristics of biochar

Numerous researches have shown that the biomass feedstock and carbonization process factors influence the physicochemical properties of biochar. Its morphological traits are influenced by the morphology of the raw materials and the carbonization process’s treatment techniques. Although the biochars produced by carbonizing various raw materials have various physical and chemical characteristics, their general compositions follow similar rules and they are all primarily made of carbon with doping of other elements.

The surface structure and pore structure of biochar, which are closely correlated with the carbonization temperature, are the primary manifestations of its physical qualities. Amorphous carbon with aromatic carbon structures gradually form at lower temperatures (around 400 °C); between 400 and 800 °C, aromatic structures are connected to form a relatively regular Layered structure, though the layers are still randomly arranged; and at higher temperatures (above 2000 °C), a more regular three-dimensional graphite structure can be further generated. The surface structure of biochar can be more fully described using XRD. Biochar is mostly made of amorphous carbon with a local crystal structure, according to the characterisation results of XRD [13]. The layers are joined to one another in the plane and resemble the layered stacking structure of graphene, although they are stacked arbitrarily [14]. As the carbonization temperature rises, more orderly stacking structures and an increase in the content of the carbon crystal structure are observed. The most significant element influencing the structure of all pyrolysis conditions is generally the greatest pyrolysis temperature for the creation of biochar. The structure of biochar is also influenced by additional pyrolysis factors, such as residence time, pressure, atmosphere, etc., however these factors are much lower than the pyrolysis temperature. By using BET measurements, the precise surface area data of biochar may be identified. The Tomczyk et al. [15] use BET analysis demonstrated that slow pyrolysis biochar has a greater specific surface area than fast pyrolysis biochar. However, Brown et al. [16] research found that when the carbonization temperature approached 750 °C, the specific surface area of biochar increased significantly. Biochar has significant application potential in the field of soil improvement because to its pore structure, which can effectively enhance soil porosity and improve soil water holding capacity. The carbonization temperature is also directly connected to the pore structure of biochar. In general, the relationship between the specific surface area and the biochar’s pore volume is positive. Additionally, prior research has demonstrated that micropores (pore size < 2 nm) have the biggest influence on the material’s specific surface area, adsorption efficiency, and other properties. The energy and reaction time needed for pore formation during the carbonization process are also obtained by the biochar feedstock as the carbonization temperature and reaction time rise [17].

The chemical makeup of biomass source materials has a significant impact on the chemical characteristics of biochar. There is no definite and agreed-upon understanding of the chemical characteristics of biochar due to the complexity and diversity of its constituent ingredients. The fixed carbon content in biochar is between 40% and 60%, followed by O, N, and H, and is the element with the highest concentration as a carbon material [18]. The composition of other elements is influenced by the raw material itself [12]. According to certain research, biochar made from raw materials such as wheat straw, corn straw, bagasse, and other herbal biomass is more likely to contain inorganic components than biochar made from wood [19-22]. Temperature will also have an impact on the elemental makeup of biochar. Metal components as Mg, Ca, P, K, Cu, Zn, Fe, and Mn have become more abundant in pig dung and straw biochar as the carbonization temperature has risen [23]. Biochar’s chemical properties are generally based on the characteristics of the raw material from which it is made, and because it contains a lot of fixed carbon and nutrients like N, P, and K as well as other trace elements, it has better soil application potential and carbon sequestration and emission reduction potential (Figure 2).

Figure 2:Physicochemical properties of biochar.

Effect of straw biochar application on soil physical properties

Numerous studies have shown that adding biochar to soil can enhance its physical and chemical characteristics. After being pyrolyzed at a high temperature, biochar has a large specific surface area and a rich pore structure that can effectively increase soil’s ability to retain water, especially sandy soil with a rough texture [3]. According to the study, applying 5% and 25% biochar to sandy soil, respectively, boosted soil water retention by 370% and 260% compared to the blank control. According to Abrol et al. [24], the high specific surface area and many pores of biochar resulted in a decrease in the soil’s water permeability and a correspondingly enhanced water retention period. Biochar can increase soil permeability, strengthen soil structure, enrich soil porosity, decrease soil bulk density, remove compaction, and promote the development of plant roots in addition to increasing soil’s ability to hold water [25- 28]. Laird et al. [29] findings show that adding biochar to the soil can dramatically lessen how compact it is. They found that adding 25g·kg-1 of biochar can reduce density by 0.19g·cm³.

Effect of straw biochar application on Soil Nutrients

For crops to grow normally, soil nutrients are a crucial requirement. The nutrient content of the soil can be successfully increased by adding biochar, which also aids in plant growth [30]. According to studies, biochar is a significant source of N, P, K, and other micronutrients. Particularly, livestock dung biochar has high levels of minerals that can support the growth of microorganisms and crops [4,5]. The key cations (K, Mg, Ca, Mn, Zn, and Cu) necessary for plant growth can be more readily available in soil after applying biochar [31]. The amount of organic matter and organic carbon in the soil can also be increased by adding biochar [32]. According to Liang et al. [33], biochar can adsorb small-sized organic molecules from the soil using its own pore structure and encourage the aggregation of these molecules. create organic soil material. After adding biochar to the soil for 5 months, Meng et al. [34] discovered that SOC dramatically increased. Additionally, the soil fertility can be effectively increased by the soluble organic carbon added by biochar. Biochar’s rich functional groups and holes on the surface can also increase the availability of soil nutrients, improve nutrient uptake, and boost nutrient retention in the soil [35].

Effect of straw biochar application on crop growth

The effect of biochar on crops is a crucial area of biochar study. Numerous studies conducted recently have supported the impact of applying biochar to the soil on crops [29,36-38]. Studies on biochar’s impacts on crops are now primarily short-term in nature and do not include long-term data, especially at the field scale. Through the addition of nutrients and physical components, biochar can change the pH of acidic soil, increase soil nutrient availability over time, and reduce nutrient loss [39,40]. It can also reduce agricultural non-point source pollution, increase fertilizer use efficiency, and decrease fertilizer application in agricultural production [41- 43]. According to several research, biochar can enhance soil nitrogen fixation [44,45] and plant uptake of nitrogen [46]. Biochar greatly increased crop output in the aforementioned experiments, particularly in pot experiments. However, in other studies, biochar had no discernible impact on crop yields. For instance, there was no discernible change in crop yield between various treatments in certain tests with lower biochar application rates [47]. There is still a dearth of systematic study on the long-term effects of biochar application on crops, and it is unclear when biochar will start to affect crops in the field or how much it will affect agricultural yield. The coupling of various crop species, soil conditions, biochar types, and carbonization process parameters is mostly to blame for this, which makes the influencing elements excessively complex and fraught with uncertainty. The unknown elements are magnified in longterm applications. Therefore, how to choose appropriate biochar in various soils to create a good influence on soil and crops is a crucial problem, and it is also one of the barriers preventing the growth of the biochar industry and the widespread use of biochar.

Carbon fixation and storage capacity of biochar

The greatest share of the world’s greenhouse gas emissions, CO₂, are attributable to human activity, which has increased pressure to reduce global warming and greenhouse gas emissions. Soil is an essential component of nature and a significant source of greenhouse gas emissions that contribute to climate change and global warming. 20% of all CO₂ emissions are caused by the respiration of soil and plant roots [48]. However, agricultural soil is also one of the most significant carbon sinks and a key tool for lowering greenhouse gas emissions and stabilizing CO₂ levels. In the absence of carbon sequestration, plants will naturally release the CO₂ they have taken in during photosynthesis back into the atmosphere through respiration and mineralization. Utilizing carbonization technology, biomass wastes like plants and cereals can be transformed into fixed carbon. The majority of CO₂ can be fixed once it has been added to the soil, and only approximately 5% can be turned into CO₂ through mineralization, which has a significant potential for carbon sequestration [49]. Biochar has a highly aromatic structure and great corrosion resistance due to high temperature carbonization. It can combine with soil minerals to form aggregates, stay in the soil for a long time, and aid in the storage of carbon.

Emission reduction capacity and carbon reduction capacity of biochar

Emission reduction capacity of biochar:The fundamental way that biochar’s capacity to reduce emissions is demonstrated is by the fact that, when applied to soil, it enhances the amount of nutrients and organic matter present, decreases the need for chemical fertilizers, and effectively prevents N₂O emissions from chemical fertilizers. decrease. N₂O has a 298-fold greater potential to cause global warming than CO₂ as a greenhouse gas [50]. According to studies, the use of nitrogen fertilizers in agriculture has a direct impact on N₂O emissions [51]. Currently, it is thought that agricultural soils are the source of 84% of anthropogenic N₂O emissions [52]. Applying biochar to soil has been shown to reduce N₂O emissions, which may be because it speeds up denitrification or because it increases aeration, which lowers N₂O emissions during denitrification [53-55]. According to research by Alisial et al. [56], applying biochar to soil can cut N₂O emissions by as much as 64.9%. The return of sawdust biochar to the field can reduce N₂O emissions by 31.5%, according to a study by Pokharel et al. [57].

Carbon reduction capacity of biochar:The carbon reduction potential of biochar is mainly attributed to its effective suppression of CO2 and CH4 emissions, with obvious carbon reduction potential. Lehmann et al. [58] were the first to evaluate the emission reduction potential of biochar, and the evaluation results showed that, Changing from the traditional “slash-burn” agricultural farm ing mode to “slash-carbon” on a global scale will obtain a carbon sequestration and emission reduction potential of 0.19~0.21×10⁹ tC∙a^-1, It can offset 12% of the carbon emissions caused by land changes caused by human activities (1.7×109 tC∙a-1). But Lehmann’s assessment only considers the carbon sequestration capacity of biochar itself, ignoring the other aspects of biochar’s emission reduction potential. Woolf et al. [59] comprehensively considered the potential carbon sequestration potential of biochar from various applications. Its research shows that the application of biochar technology can achieve a carbon reduction potential of 1.0~1.8×10⁹ t per year, and the cumulative potential can reach 66~130×10⁹ t (calculated as CO_2e) after a hundred years. Half of the potential comes from biochar’s own carbon sequestration, about 30% comes from renewable energy production instead of fossil energy use to reduce emissions, and the rest comes from greenhouse gas emissions reductions such as CH4 and N₂O. Roberts et al. [60] selected crop straw, yard waste and energy crops, and studied the emission reduction effect of biochar preparation and soil application in the slow carbonization production process. The conclusion is that the total greenhouse gas emission reduction in the biochar production process is about 870 kgCO2e·t^-1 dry biomass raw material, and the contribution of biochar carbon sequestration is about 65%. The evaluation results of Hammond et al. [61] show that the carbon reduction potential of biochar technology using different biomass raw materials is 0.7~1.3 tCO2e∙t^-1 raw materials; through the analysis of life cycle stages, it can be seen that the largest emission reduction is the biochar itself. Carbon sequestration (40%-50%), followed by the impact of biochar on greenhouse gas emissions during agricultural production (25%-40%).

Biochar will perform the role of carbon reduction by reducing CH4 emissions in addition to conventional CO₂ emissions after being applied to the soil [62]. According to a study by Liu et al. [63], applying biochar to rice soil can cut CH₄ emissions by as much as 91.2%. The capacity of various forms of biochar to reduce carbon varies. Bamboo charcoal biochar has a lesser capacity to reduce carbon than straw biochar, which has a capacity of 51.1%. According to a study by Feng et al., adding biochar to soil can improve microbial oxidation of CH₄ and decrease CH₄ emissions while also increasing soil porosity.

Currently, a resource-use technique that is mature and effective is carbonization of agricultural waste. Carbon sequestration, trash management, and energy production can all be accomplished at once by using agricultural waste biomass for biochar manufacturing and soil application. The likelihood of carbon sequestration is good, and agricultural output is increased. Waste has a lot of application potential in the fields of environment and energy. The technology for carbonizing biomass is currently advancing quickly. The physical and chemical characteristics of biochar and its use in soil have been the subject of several investigations. It has been proven that biochar can alter soil porosity, enhance soil water holding capacity, decrease soil bulk density, improve nutrient content and fertility, and has a particular beneficial impact on fostering the growth and development of crops in the soil. Due to a variety of its own physical and chemical characteristics, biochar has excellent carbon sequestration and emission reduction potential. Through both its own carbon sequestration and its influence on greenhouse gas emissions during agricultural production, biochar can successfully offset carbon emissions brought on by human activities. The kind of biochar source material also has some bearing on how well it can sequester carbon and reduce emissions. The capacity of biomass for reducing emissions and sequestering carbon can be maximized with the right biomass raw materials. In order to maximize carbon sequestration and emission reduction, the right biochar should be chosen before being applied to the area. However, there is currently a dearth of pertinent economic and environmental impact studies on the use of biochar for carbon sequestration and emission reduction. Theoretically, field carbon sequestration and emission reduction offer enough support, encouraging the quick development and widespread use of biochar returning to fields.

This work was supported by Qilu University of Technology (Shandong Academy of Sciences)-University (Academy) Local Industry- University-Research Collaborative Innovation Fund Project (No. 2020CXY-44).

No conflict of interest.

1. Hossain MZ, Bahar MM, Sarkar B, Donne SW, Ok YS, et al. (2020) Biochar and its importance on nutrient dynamics in soil and plant. Biochar 2(4): 379-420.
2. Blanco Canqui H (2017) Biochar and Soil Physical Properties. Soil Science Society of America Journal 81(4): 687-711.
3. Xue P, Fu Q, Li T, Liu D, Hou R, et al. (2022) Effects of biochar and straw application on the soil structure and water-holding and gas transport capacities in seasonally frozen soil areas. J Environ Manage, 301(113943).
4. An N, Zhang L, Liu Y, Shen S, Li N, et al. (2022) Biochar application with reduced chemical fertilizers improves soil pore structure and rice productivity. Chemosphere, 298(134304).
5. Adekiya AO, Agbede TM, Olayanju A, Ejue WS, Adekanye TA, et al. (2020) Effect of Biochar on Soil Properties, Soil Loss, and Cocoyam Yield on a Tropical Sandy Loam Alfisol. ScientificWorldJournal, 2020(9391630).
6. Woolf D, Lehmann J, Lee DR (2016) Optimal bioenergy power generation for climate change mitigation with or without carbon sequestration. Nat Commun, 7(13160).
7. Han J, Zhang A, Kang Y, Han J, Yang B, et al. (2022) Biochar promotes soil organic carbon sequestration and reduces net global warming potential in apple orchard: A two-year study in the Loess Plateau of China. Sci Total Environ, 803(150035).
8. Kwon G, Bhatnagar A, Wang H, Kwon EE, Song H (2020) A review of recent advancements in utilization of biomass and industrial wastes into engineered biochar. Journal of Hazardous Materials, 400(123242).
9. Seow YX, Tan YH, Mubarak N, Kansedo J, Khalid M, et al. (2021) A review on biochar production from different biomass wastes by recent carbonization technologies and its sustainable applications. Journal of Environmental Chemical Engineering, 107017.
10. Dai L, Wang Y, Liu Y, He C, Ruan R, et al. (2020) A review on selective production of value-added chemicals via catalytic pyrolysis of lignocellulosic biomass. Sci Total Environ, 749(142386).
11. Kumar A, Saini K, Bhaskar T (2020) Hydochar and biochar: production, physicochemical properties and techno-economic analysis. Bioresource Technology, 310(123442).
12. Mukome FN, Zhang X, Silva LC, Six J, Parikh SJ (2013) Use of chemical and physical characteristics to investigate trends in biochar feedstocks. Journal of agricultural food chemistry 61(9): 2196-2204.
13. Marsh H, Reinoso FR (2006) Activated carbon. Elsevier.
14. Bansal RC, Goyal M (2005) Activated carbon adsorption. CRC press.
15. Tomczyk A, Sokołowska Z, Boguta P (2020) Biochar physicochemical properties: pyrolysis temperature and feedstock kind effects. Reviews in Environmental Science and Bio/Technology 19(1): 191-215.
16. Brown RA, Kercher AK, Nguyen TH, Nagle DC, Ball WP (2006) Production and characterization of synthetic wood chars for use as surrogates for natural sorbents. Organic Geochemistry 37(3): 321-333.
17. Blackwell P, Riethmuller G, Collins M (2009) Biochar for environmental management: Science and technology.
18. Brown T, Wright M, Brown R (2011) Estimating profitability of two biochar production scenarios: slow pyrolysis vs fast pyrolysis. Bioproducts and Biorefining 5(1): 54-68.
19. Nwajiaku IM, Olanrewaju JS, Sato K, Tokunari T, Kitano S, et al. (2018) Change in nutrient composition of biochar from rice husk and sugarcane bagasse at varying pyrolytic temperatures. International Journal of Recycling of Organic Waste in Agriculture 7(4): 269-276.
20. Tatarkova V, Hiller E, Vaculik M (2013) Impact of wheat straw biochar addition to soil on the sorption, leaching, dissipation of the herbicide (4-chloro-2-methylphenoxy)acetic acid and the growth of sunflower (Helianthus annuus). Ecotoxicol Environ Saf 92: 215-221.
21. Rafiq MK, Bachmann RT, Rafiq MT, Shang Z, Joseph S, et al. (2016) Influence of Pyrolysis Temperature on Physico-Chemical Properties of Corn Stover (Zea mays L.) Biochar and Feasibility for Carbon Capture and Energy Balance. PLoS One 11(6): 0156894.
22. Domingues R, Trugilho P, Silva C (2017) Properties of biochar derived from wood and high-nutrient biomasses with the aim of agronomic and environmental benefits. PLoS One 12(5): 0176884.
23. Zhao L, Cao X, Masek O, Zimmerman A (2013) Heterogeneity of biochar properties as a function of feedstock sources and production temperatures. J Hazard Mater 256-257:1-9.
24. Abrol V, Ben Hur M, Verheijen FG, Keizer JJ, Martins MA, et al. (2016) Biochar effects on soil water infiltration and erosion under seal formation conditions: rainfall simulation experiment. Journal of Soils Sediments 16(12): 2709-2719.
25. Petersen CT, Hansen E, Larsen HH, Hansen LV, Ahrenfeldt J, et al. (2016) Pore-size distribution and compressibility of coarse sandy subsoil with added biochar. European Journal of Soil Science 67(6): 726-736.
26. Kamau S, Karanja NK, Ayuke FO, Lehmann J (2019) Short-term influence of biochar and fertilizer-biochar blends on soil nutrients, fauna and maize growth. Biology and Fertility of Soils 55(7): 661-673.
27. Xiu L, Zhang W, Wu D, Sun Y, Zhang H, et al. (2021) Biochar can improve biological nitrogen fixation by altering the root growth strategy of soybean in Albic soil. Sci Total Environ 773(144564).
28. Backer RGM, Saeed W, Seguin P, Smith DL (2017) Root traits and nitrogen fertilizer recovery efficiency of corn grown in biochar-amended soil under greenhouse conditions. Plant and Soil 415(1): 465-477.
29. Laird DA, Fleming P, Davis DD, Horton R, Wang B, et al. (2010) Impact of biochar amendments on the quality of a typical Midwestern agricultural soil. Geoderma 158(3-4): 443-449.
30. Zhou Z, Gao T, Van Zwieten L, Zhu Q, Yan T, et al. (2019) Soil Microbial Community Structure Shifts Induced by Biochar and Biochar‐Based Fertilizer Amendment to Karst Calcareous Soil. Soil Science Society of America Journal 83(2): 398-408.
31. Zhang Y, Wang J, Feng Y (2021) The effects of biochar addition on soil physicochemical properties: A review. Catena, 202.
32. Zygourakis K (2017) Biochar soil amendments for increased crop yields: how to design a “designer” biochar. AIChE Journal 63(12): 5425-5437.
33. Liang B, Lehmann J, Sohi SP, Thies JE, O’neill B, et al. (2010) Black carbon affects the cycling of non-black carbon in soil. Organic Geochemistry 41(2): 206-213.
34. Meng Y, Zhao C, Li X, Xu Q, Chen L, et al. (2018) Effects of biochar on soil organic carbon pools in phaeozem. Acta Agriculturae Universitatis Jiangxiensis 40(6): 1340-1347.
35. Asai H, Samson BK, Stephan HM, Songyikhangsuthor K, Homma K, et al.(2009) Biochar amendment techniques for upland rice production in Northern Laos. Field Crops Research 111(1-2): 81-84.
36. Zhang A, Cheng G, Hussain Q, Zhang M, Feng H, et al. (2017) Contrasting effects of straw and straw–derived biochar application on net global warming potential in the Loess Plateau of China. Field Crops Research 205: 45-54.
37. Cui YF, Meng J, Wang QX, Zhang WM, Cheng XY, et al. (2017) Effects of straw and biochar addition on soil nitrogen, carbon, and super rice yield in cold waterlogged paddy soils of North China. Journal of Integrative Agriculture 16(5): 1064-1074.
38. Zhang A, Bian R, Pan G, Cui L, Hussain Q, et al. (2012) Effects of biochar amendment on soil quality, crop yield and greenhouse gas emission in a Chinese rice paddy: A field study of 2 consecutive rice growing cycles. Field Crops Research 127:153-160.
39. Beck DA, Johnson GR, Spolek GA (2011) Amending greenroof soil with biochar to affect runoff water quantity and quality. Environ Pollut 159(8-9): 2111-2118.
40. Foereid B, Lehmann J, Major J (2011) Modeling black carbon degradation and movement in soil. Plant and Soil 345(1-2): 223-236.
41. Arif M, Ilyas M, Riaz M, Ali K, Shah K, et al. (2017) Biochar improves phosphorus use efficiency of organic-inorganic fertilizers, maize-wheat productivity and soil quality in a low fertility alkaline soil. Field Crops Research 214: 25-37.
42. Chen L, Li X, Peng Y, Xiang P, Zhou Y, et al. (2022) Co-application of biochar and organic fertilizer promotes the yield and quality of red pitaya (Hylocereus polyrhizus) by improving soil properties. Chemosphere 294: 133619.
43. Uzoma KC, Inoue M, Andry H, Fujimaki H, Zahoor A, et al. (2011) Effect of cow manure biochar on maize productivity under sandy soil condition. Soil Use and Management 27(2): 205-212.
44. Zheng J, Luan L, Luo Y, Fan J, Xu Q, et al. (2022) Biochar and lime amendments promote soil nitrification and nitrogen use efficiency by differentially mediating ammonia-oxidizer community in an acidic soil. Applied Soil Ecology, 180.
45. Liao X, Mao S, Chen Y, Zhang J, Muller C, et al. (2022) Combined effects of biochar and biogas slurry on soil nitrogen transformation rates and N2O emission in a subtropical poplar plantation. Sci Total Environ, 157766.
46. Liu J, Jiang B, Shen J, Zhu X, Yi W, et al. (2021) Contrasting effects of straw and straw-derived biochar applications on soil carbon accumulation and nitrogen use efficiency in double-rice cropping systems. Agriculture, Ecosystems & Environment, 311.
47. Tammeorg P, Simojoki A, Mäkelä P, Stoddard FL, Alakukku L, et al. (2013) Biochar application to a fertile sandy clay loam in boreal conditions: effects on soil properties and yield formation of wheat, turnip rape and faba bean. Plant and Soil 374(1-2): 89-107.
48. Parry ML, Canziani O, Palutikof J, Van Der Linden P, Hanson C (2007) Climate change 2007-impacts, adaptation and vulnerability: Working group II contribution to the fourth assessment report of the IPCC. Cambridge University Press.
49. Lehmann JJN (2007) A handful of carbon. Nature 447(7141): 143-144.
50. Change IC (2014) Synthesis Report. Contribution of working groups I. II and III to the fifth assessment report of the intergovernmental panel on climate change, 151(10.1017).
51. Gao B, Ju X, Su F, Meng Q, Oenema O, et al. (2014) Nitrous oxide and methane emissions from optimized and alternative cereal cropping systems on the North China Plain: a two-year field study. Sci Total Environ, 472(112-124).
52. Smith P, Martino D, Cai Z, Gwary D, Janzen H, et al. (2008) Greenhouse gas mitigation in agriculture. Philosophical transactions of the royal Society B: Biological Sciences 363(1492): 789-813.
53. Case SDC, Mcnamara NP, Reay DS, Whitaker J (2012) The effect of biochar addition on N₂O and CO₂ emissions from a sandy loam soil – The role of soil aeration. Soil Biology and Biochemistry, 51(125-134).
54. Van Zwieten L, Kimber S, Morris S, Downie A, Berger E, et al. (2010) Influence of biochars on flux of N₂O and CO₂ from Ferrosol. Soil Research 48(7): 555-568.
55. Li W, Xie H, Ren Z, Li T, Wen X, et al. (2022) Response of N₂O emissions to N fertilizer reduction combined with biochar application in a rain-fed winter wheat ecosystem. Agriculture, Ecosystems & Environment, 333.
56. Sial TA, Shaheen SM, Lan Z, Korai PK, Ghani MI, et al. (2022) Addition of walnut shells biochar to alkaline arable soil caused contradictory effects on CO₂ and N₂O emissions, nutrients availability, and enzymes activity. Chemosphere 293(133476).
57. Pokharel P, Kwak JH, Ok YS, Chang SX (2018) Pine sawdust biochar reduces GHG emission by decreasing microbial and enzyme activities in forest and grassland soils in a laboratory experiment. Sci Total Environ, 625(1247-1256).
58. Lehmann J, Gaunt J, Rondon M (2006) Bio-char Sequestration in Terrestrial Ecosystems – A Review. Mitigation and Adaptation Strategies for Global Change 11(2): 403-427.
59. Woolf D, Amonette JE, Street-Perrott FA, Lehmann J, Joseph S (2010) Sustainable biochar to mitigate global climate change. Nature communications 1(1): 1-9.
60. Roberts KG, Gloy BA, Joseph S, Scott NR, Lehmann J (2010) Life cycle assessment of biochar systems: estimating the energetic, economic, and climate change potential. Environmental science technology 44(2): 827-833.
61. Hammond J, Shackley S, Sohi S, Brownsort P (2011) Prospective life cycle carbon abatement for pyrolysis biochar systems in the UK. Energy policy 39(5): 2646-2655.
62. Jeffery S, Verheijen FGA, Kammann C, Abalos D (2016) Biochar effects on methane emissions from soils: A meta-analysis. Soil Biology and Biochemistry, 101(251-258).
63. Liu Y, Yang M, Wu Y, Wang H, Chen Y, et al. (2011) Reducing CH₄ and CO₂ emissions from waterlogged paddy soil with biochar. Journal of Soils and Sediments 11(6): 930-939.