Abstract：
Increasing soil organic carbon (SOC) stocks in agricultural soils removes carbon dioxide from the atmosphere and contributes towards achieving carbon neutrality. For farmers, higher SOC levels have multiple benefits, including increased soil fertility and resilience against drought-related yield losses. However, increasing SOC levels requires agricultural management changes that are associated with costs. Private soil carbon certificates could compensate for these costs. In these schemes, farmers register their fields with commercial certificate providers who certify SOC increases. Certificates are then sold as voluntary emission offsets on the carbon market. In this paper, we assess the suitability of these certificates as an instrument for climate change mitigation. From a soils\' perspective, we address processes of SOC enrichment, their potentials and limits, and options for cost-effective measurement and monitoring. From a farmers\' perspective, we assess management options likely to increase SOC, and discuss their synergies and trade-offs with economic, environmental and social targets. From a governance perspective, we address requirements to guarantee additionality and permanence while preventing leakage effects. Furthermore, we address questions of legitimacy and accountability. While increasing SOC is a cornerstone for more sustainable cropping systems, private carbon certificates fall short of expectations for climate change mitigation as permanence of SOC sequestration cannot be guaranteed. Governance challenges include lack of long-term monitoring, problems to ensure additionality, problems to safeguard against leakage effects, and lack of long-term accountability if stored SOC is re-emitted. We conclude that soil-based private carbon certificates are unlikely to deliver the emission offset attributed to them and that their benefit for climate change mitigation is uncertain. Additional research is needed to develop standards for SOC change metrics and monitoring, and to better understand the impact of short term, non-permanent carbon removals on peaks in atmospheric greenhouse gas concentrations and on the probability of exceeding climatic tipping points.
摘要：
农业土壤中土壤有机碳（SOC）储量的增加可从大气中去除二氧化碳，并有助于实现碳中和。对于农民来说,更高的SOC水平有多重好处，包括提高土壤肥力和抵御干旱相关产量损失的能力。然而,提高SOC水平需要与成本相关的农业管理变革。私人土壤碳证书可以补偿这些成本。在这些方案中,农民向证明SOC增加的商业证书提供商注册他们的田地。然后，证书作为自愿排放补偿在碳市场上出售。在本文中,我们评估这些证书作为缓解气候变化工具的适用性。从土壤的角度来看，我们讨论了SOC富集的过程，他们的潜力和局限性，以及具有成本效益的测量和监测的选项。从农民的角度来看，我们评估可能增加SOC的管理选择，并讨论它们与经济的协同作用和权衡，环境和社会目标。从治理的角度来看，我们满足在防止泄漏影响的同时保证额外性和持久性的要求。此外，我们解决合法性和问责制的问题。虽然增加SOC是更可持续种植系统的基石，由于无法保证SOC封存的持久性，私人碳证书未达到缓解气候变化的期望。治理挑战包括缺乏长期监测，确保额外性的问题，防止泄漏影响的问题，如果重新发出存储的SOC，则缺乏长期问责制。我们得出的结论是，基于土壤的私人碳证书不太可能提供归因于它们的排放抵消，并且它们对缓解气候变化的好处是不确定的。需要额外的研究来制定SOC变化指标和监测的标准，为了更好地理解短期的影响，大气温室气体浓度峰值和超过气候临界点的可能性上的非永久性碳去除。
