专家建议
何时在LCA中加入生物碳
Part 1 in a series on biogenic carbon accounting for wood products – an overview of biogenic carbon accounting practices as defined by international standards
Biogenic carbon accounting practices are described in the international standard, ISO 21930, which governs environmental product declarations (EPDs) for construction products.1 Biogenic carbon is defined as “carbon derived from… material of biological origin excluding material embedded in geological formations or transformed to fossilized material and excluding peat.“在木结构建筑产品的背景下, this is the carbon sequestered by the tree as it grows that continues to be stored in the wood product over its lifetime.
ISO 21930第7节.2.7:
Bio-based materials originating from renewable resources… contain biogenic carbon. The mass flows to and from nature and biogenic carbon removal(s) and emissions throughout the product system shall be reported as a flow of biogenic carbon…”
具体地说, it states that biogenic carbon entering the system shall be characterized with a factor of -1 (i.e., 减少碳排放), which represents the removal of carbon from the atmosphere that occurs as a tree grows. 当材料燃烧或衰变时, some or all of that stored carbon is released back to the atmosphere and must be characterized with a factor of +1 (i.e.碳排放). 类似的, 任何时候含有生物碳的物质离开系统, 碳的特征系数也是+1.
简单地说, 当生物碳进入一个系统, it is reported as a negative value; when it leaves the system, 它被报告为正值. Using this “-1 in/+1 out” accounting practice in accordance with ISO 21930 is what designers commonly mean when they say they are “including biogenic carbon.”
The standard language above references “bio-based materials originating from renewable resources.这一点在后面的同一章节中得到了重申:
对于木材，生物碳的特征可能是-1 kg CO2e /公斤有限公司2 biogenic carbon flow when entering the product system only when the wood originates from sustainably managed forests (see also NOTE 2 in 7.2.11).
第7节注2.2.11个州:
The concept of sustainably managed forests is linked but not limited to respective certification schemes. Other evidences such as national reporting under the United Nations Framework Convention on Climate Change (UNFCCC) can be used to identify forests with stable or increasing forest carbon stocks.
根据这个定义， 所有的你.S. and Canadian lumber is considered to be sourced from sustainably managed forests due to the fact that the forest carbon stock in each country has been increasing since 1990 when reporting began. (U.S. 数据是根据美国环保署的美国化学品清单.S. 2021年发布的《皇冠99hg现金网》报告.2 Canadian data is per the 国家 Inventory Report of Greenhouse Gas Sources and Sinks in Canada.3) Additionally, data from the USDA’s Forest Inventory and Analysis Program shows that U.S. forestland area has been stable for more than 100 years and that the volume of standing inventory in those forests has increased 60 percent in the past 60 years.4
因此, based on the international standards that govern biogenic carbon accounting practices, it is appropriate to report the biogenic carbon flows as part of the LCA. 所有来自美国的木材都是如此.S. 加拿大则是基于国家报告. 来自其他国家的木材, designers may either specify lumber sourced in accordance with standards developed by third-party certification programs5根据第7条.2.11, or rely on UNFCCC national reporting data for that country of origin. For more information on LCA and the sustainability of wood buildings, see the expert tip, 整个建筑生命周期评估导论:基础.
关于如何在LCA中包含生物碳，请参阅 第2部分. 有关WBLCA工具如何计算生物碳的详细信息，请参见 第3部分. For a discussion on the additional benefits of long-term biogenic carbon storage, see 第4部分.
额外的资源
萨拉查,我. 碳领导力论坛. 5月(2020). 木材碳研讨会:LCA如何处理木材.
认为木材. 2月(2021). 了解隐含碳在气候智能型建筑中的作用.
1 国际标准化组织. (2017). 可持续性 in buildings and civil engineering works – Core rules for environmental product declarations of construction products and services (ISO 21930:2017).
2 U库存.S. 温室气体排放和汇表6-10.
3 国家 Inventory Report 1990-2019: Greenhouse Gas Sources and Sinks in Canada表6-1.
4Oswalt,年代. N.迈尔斯，P. D.皮尤，S. A., & 史密斯,W. B. (2018). 美国森林资源, 2017: A Technical Document Supporting the Forest Service 2020 Update of the RPA Assessment. U.S. 农业部，林务局.
5Note that this includes products sourced in accordance with responsible sourcing standards, such as the FSC Controlled Wood Standard or the SFI Fiber Sourcing Standard, 以及监管链标准, 比如FSC监管链标准, 监管链标准, 或PEFC监管链标准.
