木材是減少 AEC 排放的關鍵
Woods As Key To Reduce The AEC’s Emissions
聯合國的可持續發展目標 (SDG) 長期以來一直要求企業解決有關森林砍伐及其供應鏈的問題。在 AEC 環境中，木材通常被視為更具可持續性的材料，尤其是與具有“骯髒”和高排放製造工藝的鋼或混凝土相比。但隨著森林砍伐、非法採伐和全球變暖等問題，木材真的是一種環保材料嗎？
隨著十年來的新建築技術，建築行業已經趕上了木材替代品的趨勢，這也成為行業綠色運動的代表：高層木材或通常也稱為 plyscrapers。該術語被定義為主要由木材或交叉層壓木材 (CLT) 建造的至少有 14 層或 50m 高的建築物。這些木質高層建築已被證明可以減少溫室氣體排放和化石燃料的消耗，比混凝土和鋼材更堅固，建造速度更快，並且在發生火災時更安全，因為 CLT 會形成一層炭，可以保護它的內部。此前，CLT早在1990年就已在奧地利、德國等歐洲國家的低層建築中受到青睞，而其好處早已得到歐盟的認可。考慮到所有這些品質，到 2024 年，CLT 市場的發展軌跡預計將達到 16 億美元。
雖然由鋼樑支撐的一平方米樓面空間可以排放 40 公斤的二氧化碳並需要高達 516 兆焦的能量，但其混凝土對應物的二氧化碳排放量可以降低 68%，每平方米排放 27 公斤的二氧化碳和 290 兆焦的能量。相反，使用木樑作為替代方案僅排放 4kg 的二氧化碳，需要 80MJ 的能量，僅為傳統鋼樑的 10%。在整個生命週期中，木結構建築的排放率比鋼結構建築低近 75%。最重要的是，使用木質替代品作為建築材料還可以增加碳封存，其中樹木在存活時捕獲的碳現在被困在裡面並永遠儲存在原木中，而不是釋放回大氣中。該過程被認為對幫助全球變暖非常有益，因為一立方米的木材可以捕獲超過一噸的二氧化碳。如果做得好，木材工業可以通過提高森林生長速度和最大限度地減少行業製造過程中的排放來增加全球的碳捕獲量，同時也有助於循環經濟，因為整個樹木生產過程幾乎沒有殘留物。當樹木被收割並切成原木和木材時，剩餘的木屑和刨花被收集起來，並在燃燒時變成纖維板、木漿甚至能量。
很明顯，木材將繼續成為 AEC 行業的熱門參與者，然而，我們處理這些材料的方式將決定它如何幫助該行業變得更加環保。使用可持續木材，這意味著木材“以負責任的方式採伐並立即更換”，並在每個步驟中管理其供應鏈可以確保木材行業的效率和透明度。由於該行業的供應鏈可能非常複雜且容易受騙，因此在整個供應鏈中追踪木材的能力對於確保木材來自合法來源極為重要。木材經銷商通常會從許多不同的伐木者和鋸木廠購買木材，然後再將它們出售給製造商。在這個過程中，這些樹會混在一起，失去它們的身份和來源。
一種可能的解決方案是提供法律文件，允許製造商和最終客戶追溯這些原材料的來源。這些文件可以採取許可證、可持續森林管理證書、原產地證書、合法性、出口文件、運輸證書等形式。然而，隨著一些國家虛假文件的興起，企業開始將注意力轉移到區塊鍊和 RFID（射頻識別）。有了 RFID，每棵樹都會被標記上電子存儲的信息，甚至可以從更遠的距離讀取這些信息。然後這些信息可以更新到中央數據庫並轉換為區塊鏈，其中信息現在是安全且不可更改的，同時也可以通過系統訪問。另一方面，還開發了一些技術，包括 DNA 指紋識別、DNA 繪圖和電子條形碼，作為檢查木材供應鏈的一種方式。這些維持透明鏈的努力將對企業施加巨大壓力，避免使用來源不明的產品以及非法切割，並引導它們實現經濟可持續發展。
目前，每年採伐的木材僅佔建築業年增長的 20%。通過將這個數字提高到 34%，我們可以將鋼鐵和混凝土排放的全球二氧化碳排放量減少多達 31%，同時還將全球化石燃料消耗量減少多達 19%。 Tree 是完美的碳回收機器。通過隨著時間的推移負責任地收穫它們，並在建築或替代材料中賦予提取的原木第二次生命，我們可以將二氧化碳捕獲在這些原木中，並穩步減少大氣中的二氧化碳含量。
The United Nation’s Sustainable Development Goals (SDGs) have long challenged businesses to address their issues regarding deforestation and its supply chain. In the AEC settings, woods are often seen as more sustainable materials, especially when compared to steel or concrete with their ‘dirty’ and high emission manufacturing process. But with issues of deforestation, illegal logging, and global warming, does wood really is an eco-friendly material?
Woods are used as lumber or other solid wood products in construction. It’s often used to repair and remodel home construction, create furniture, papers, as well as hygiene products. More recently, woods have also been used to create wood-based textiles and other plastic alternatives. As a highly versatile material, the use of wood has been increasing globally for both construction materials and greener substitutes in various industries.
The construction industry has caught up on the wood alternatives trend with the new construction techniques of the decade, which since also become the face of the green movement in the industry: high-rise timber or often also called plyscrapers. The term was defined as buildings with at least fourteen floors or 50m in height that are constructed mainly with woods or cross-laminated timber (CLT). These wood-based high-rises have been proved to reduce the GHG emissions and consumption of fossil fuel, stronger than concrete and steel, quicker to build, and safer in event of a fire as the CLT will form a layer of char that would protect its interior. Previously, the use of CLT has been favored in low-rise buildings in European countries like Austria and Germany as early as 1990, while its benefits have long been endorsed by the EU. With all these qualities in mind, the trajectory of the CLT market is expected to reach USD 1,6 billion by 2024.
While one square meter of floor space that is supported by steel beams could emit 40kg of carbon dioxides and required up to 516 MJ of energy, its concrete counterpart could release 68% lower at 27kg of carbon dioxides and 290 MJ of energy per square meter. On the contrary, the use of wooden beams as an alternative only emits 4kg of CO2 and requires 80MJ of energy, a mere 10% of the traditional steel beam. Throughout its life cycle, the emission rate of wood-constructed buildings is almost 75% lower than steel-constructed ones. On top of that, using wood-based substitutes as construction materials could also increase carbon sequestration, in which the carbon that is captured by the trees when it’s alive is now trapped inside and forever stored inside the log instead of released back to the atmosphere. The process is believed to be highly beneficial in helping global warming since one cubic meter of wood can trap more than one ton of carbon dioxide. When done right, the wood industry can increase global’s carbon capture by increasing the forest growth rate and minimizing emissions during the industry’s manufacturing process, while also contributing to the circular economy since the whole tree producing process leave almost no leftovers. When the trees are harvested and cut up into logs and lumber, the residual chips and shavings are collected and turned into fiberboard, wood pulp, and even energy when burned.
It’s evident that woods would continue to be a favored player in the AEC industry, however, the way we deal with these materials would be the make or break of how it could help the industry to become more eco-friendly. Using sustainable timber, which means that the woods are ‘harvested responsibly and replaced immediately’, and managing its supply chain at each of its steps could ensure efficiency and transparency of the wood industry. As the industry’s supply chain can be very complex and easily conned, the ability to trace woods throughout the whole chain is extremely important to assure that the wood came from legal sources. Wood dealers would often buy woods from many different loggers, and sawmills before selling them to manufacturers. During this process, these trees would get mixed up and lose their identity and source.
One of the possible solutions is to provide legal documents that allow manufacturers and end customers to trace back the origin of these raw materials. These documents can take the form of licensing permits, certificates of sustainable forest management, certificates of origin, legality, export documents, transportation certificate, etc. However, with the rise of false documents in some countries, businesses have started to shift their attention to blockchain and RFID (Radio Frequency Identification). With RFID, every tree would be tagged with electronically stored information that could be read even from farther distances. These pieces of information could then be updated into a central database and converted into blockchains, in which the information is now secured and unchangeable, while also accessible through the system. On the other hand, some technologies including DNA fingerprinting, DNA mapping, and electronic barcoding have also been developed as a way to check the wood supply chain. These efforts in maintaining a transparent chain would put strong pressure on businesses to avoid using products from unknown sources as well as illegal cutting and lead them to economic sustainability instead.
Currently, the yearly harvested wood accounts for only 20% of the construction sector’s annual growth. By increasing this number to 34%, we could reduce up to 31% of the global CO2 emission that was emitted by steel and concrete, while also reducing global fossil fuel consumption by up to 19%. Tree works as the perfect carbon recycler machine. By responsibly harvesting them over time, and giving the extracted log second lives both in construction or as alternative materials, we can trap the CO2 inside these logs and steadily reduce the amount of carbon dioxide in the atmosphere.
Cao, L. (2021, June 15). Could Tall Wood construction be the future of high-rise buildings? ArchDaily. Retrieved March 17, 2022, from https://www.archdaily.com/924341/could-tall-wood-construction-be-the-future-of-high-rise-buildings
Figorilli, S. (2019, June). Blockchain technology could improve traceability of wood through the supply chain. Science for Environment Policy. Retrieved March 17, 2022, from https://ec.europa.eu/environment/integration/research/newsalert/pdf/blockchain_technology_could_improve_traceability_of_wood_through_the_supply_chain_527na1_en.pdf
Jafs, M., & Butz, C. (2021, May 24). Wood products are a climate change solution. ESG Clarity. Retrieved March 17, 2022, from https://esgclarity.com/wood-products-are-a-climate-change-solution/
Sustainable Supply Chains. ITTO International Tropical Timber Organization. (n.d.). Retrieved March 17, 2022, from https://www.itto.int/economic_market/supply_chains/
Where do the products come from? Sustainable Forest Products. (2016). Retrieved March 17, 2022, from https://sustainableforestproducts.org/sites/default/files/2016-09/Traceability.pdf
Wikimedia Foundation. (2021, August 8). Plyscraper. Wikipedia. Retrieved March 17, 2022, from https://en.wikipedia.org/wiki/Plyscraper
Yahoo! (2021). Timber goes green- wood is the future of ESG investment in Global Property Development"A. Yahoo! Retrieved March 17, 2022, from https://sg.style.yahoo.com/timber-goes-green-wood-future-085850199.html
About the Author
Xaveria Livienna is a freelance writer and researcher for the Taiwan Architecture and Building Center, currently pursuing an MBA degree in National Taiwan University of Science and Technology. Her main interests revolve around digital and content marketing, as well as CSR and sustainability.
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