STE全球Meta分析 | 堆肥技术对于减少氮素损失的巨大潜力
文献信息：
Zhao Shuaixiang, Schmidt Susanne, Qin Wei, Li Ji, Li Guoxue, Zhang Weifeng*. Towards the circular nitrogen economy – A global meta-analysis of composting technologies reveals much potential for mitigating nitrogen losses. Science of the Total Environment, 2020, 704: 135401. DOI: 10.1016/j.scitotenv.2019.135401
Science of the Total Environment最新（2020年）影响因子：7.963
Highlights:
Global N loss during composting averages 31.4% TN, 17.2% NH3-N and 1.4% N2O-N.
At least 30% of N loss is avoidable with existing in situ techniques.
Biochar and Mg-P salts were most effective in reducing N losses.
Adoption of improved composting requires expertise, policy and market acceptance
摘 要：堆肥是生物废弃物处理和养分循环再利用方面的一项重要技术，但会造成氮素（N）损失，降低最终产品价值及造成环境污染。而堆肥技术旨在减少堆肥过程中的氮素损失，减少负面影响。为了加深对缓解方案的深入了解，本研究根据121篇经同行评审发表文献的932个观测值进行了全球Meta分析。总体上，氮素平均损失表现为：全氮（TN）损失31.4%、NH3-N损失17.2%、N2O-N损失1.4%，其中NH3-N占TN损失的55%。影响氮素损失的主要因素是堆肥方式、生物废弃物类型和堆肥时间。氮素损失受到输入材料碳氮比（C/N）、水分含量及pH的显著影响。研究结果显示，C/N为25-30、水分含量为60–65%和pH为6.5–7.0情况下氮素损失最少。控制原料和加工条件的原位缓解技术可使氮素损失平均降低31.4%（TN）、35.4%（NH3-N）和35.8%（N2O-N）。添加生物炭和磷酸镁盐成为最有效的减少氮素损失方案，分别减少了30.2%和60.6%的TN损失、52.6%和69.4%的NH3-N损失以及66.2%和35.4%的N2O-N损失。本研究结论是，现有技术可在全球范围内固存约0.6 Tg的生物废弃物氮，这相当于非洲农田使用的化学氮肥的16%，或全球每年增加的1.58 Tg化肥氮的39%。然而，由于缺乏最佳管理措施、适当基础设施、政策和市场，导致技术应用方面受到限制。为实现支持可持续发展和循环氮素经济的节氮堆肥，利益相关者必须集体行动起来，其益处包括减少与农业相关的温室气体直接和间接排放以及促进土壤固碳。
Abstract: Composting is an important technology to treat biowastes and recycle nutrients, but incurs nitrogen (N) losses that lower the value of the final products and cause pollution. Technologies aimed at reducing N losses during composting have inconsistent outcomes. To deepen insight into mitigation options, we conducted a global meta-analysis based on 932 observations from 121 peer-reviewed published studies. Overall, N losses averaged 31.4% total N (TN), 17.2% NH3-N, and 1.4% N2O-N, with NH3-N accounting for 55% of TN losses. The primary drivers affecting N losses were composting method, type of biowaste, and duration of composting. N losses were significantly impacted by the carbon-to-nitrogen (C/N) ratio of the input materials (feedstock of nutrient dense biowastes and C-rich bulking agents), moisture content and pH. Our analysis revealed N-conserving optima with C/N ratios of 25–30, 60–65% moisture content and pH 6.5–7.0. In situ mitigation technologies that control feedstock and processing conditions reduced average N losses by 31.4% (TN), 35.4% (NH3-N) and 35.8% (N2O-N). Biochar and magnesium-phosphate salts emerged as the most effective N-conserving strategies, curbing losses of TN by 30.2 and 60.6%, NH3 by 52.6 and 69.4%, and N2O by 66.2 and 35.4% respectively. We conclude that existing technologies could preserve ~0.6 Tg of biowaste-N globally, which equates to 16% of the chemical N-fertilizer used in African croplands, or 39% of the annual global increases of 1.58 Tg fertilizer-N. However, the adoption of N-conserving technologies is constrained by a lack of knowledge of best practice, suitable infrastructure, policies and receptive markets. To realize an N-conserving composting industry that supports sustainable practices and the circular nitrogen economy, stakeholders have to act collectively. Benefits will include lowering direct and indirect greenhouse gas emissions associated with agriculture, and facilitating the recarbonization of soils.
Graphical abstract:
图1 堆肥中的TN、NH3-N和N2O-N损失
Fig. 1. TN loss (a), NH3-N loss (b) and N2O-N loss (c) in composting. Number of experimental observations is in parentheses. Dots show means, error bars represent 95% confidence intervals. Composting type: turning, aerated static and reactor; Nitrogen source type: poultry manure, pig manure, cattle manure, kitchen waste and municipal sludge; Carbon source type: sawdust, straw and by-product; Composting duration: ≤40 days, 40–80 days and > 80 days. Composting scale: pilot and commercial.
图2 C/N比、水分含量、pH与TN、NH3-N和N2O-N损失间的关系
Fig. 2. Relationship between C/N ratio (1), moisture (%) (2), pH (3) and TN loss (a), NH3-N loss (b), N2O-N loss (c). The dotted lines represent 95% confidence interval of the fitting curve. The dots represent N loss observations, the green color represents the N2O loss observations at pH above 8.0. The regressions were made with line (b-2, c-2, c-3), quadratic (a-1, a-2, b-1), quartic (c-1) and exponential (b-3) model.
图3 不同原位技术对TN、NH3-N和N2O-N损失的影响
Fig. 3. The effect of different in situ technologies on TN loss (a), NH3-N loss (b) and N2O-N loss (c). C/N RR represents C/N ratio regulation; MI represents microbial inoculation; PA represents physical additives added; CA represents chemical additives added; CO represents covering on composting; CO-Plastic represents covering with plastic-based materials; OAT represents optimized aeration rate or turning frequency. Dots show means, error bars represent 95% confidence intervals. Numbers of experimental observations are in parentheses.
图4 不同物理添加剂和化学添加剂对TN、NH3-N和N2O-N损失的影响
Fig. 4. The effect of physical additives (upper graph) and chemical additives (under graph) for TN loss (a), NH3-N loss (b) and N2O-N loss (c). Dots show means, error bars represent 95% confidence intervals. Numbers of experimental observations are in parentheses.
表 1 本Meta分析中确定的用于降低堆肥过程中TN、NH3和N2O损失的原料特性（C/N、水分、pH）最佳范围
Table 1. Optimum ranges of feedstock characteristics (C/N, moisture, pH) for lowing TN, NH3 and N2O losses during composting as identified in this meta-analysis.
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