Bill Gates’ latest contribution to the climate change debate has received混合评论。Regardless of your perspective on the multibillionaire’s role in the discussion, however, Gates highlights an important question that should, as he says, be at the heart of every climate conversation: "What’s your plan for cement?"
You might ask why cement should be a primary concern when such a huge proportion of greenhouse gas (GHG) emissions come from energy. But in reality, emissions from the energy we use to power our homes, businesses and transport only account for 55 percent of all global emissions.
We need to tackle those emissions by transitioning to renewable energy, electrifying transport and improving energy efficiency, but that alone will not reduce to zero our annual emissions, which by 2050 are projected to reach 51 billion metric tons of CO2e. As António Guterres, U.N. Secretary-General, emphasized at the Climate Ambition Summit in December, concrete plans need to be made to "reach net-zero"和"every country, city, financial institution, and company needs … to start executing them now."
Those plans can’t just be focused on energy.
更改的具体案例
Cement manufacturing alone produces a staggering2.2 billion metric tons of CO2每年，所有二氧化碳排放量中有8％。为了制作水泥，将化石燃料或废物燃烧成窑中的过热石灰并产生氧化钙 - 这是一种化学过程，导致进一步的二氧化碳排放。此外，还来自于建筑物和工业中使用的其他材料的生产，例如铁和钢，该材料在2016年占35亿吨CO2E，并且存在一个重大问题。
Steps are being用可再生能源替代品代替化石燃料窑。商业的production of steel using hydrogen rather than burning fossil fuels, for example, was piloted in 2020, demonstrating the potential of new technologies to reduce industrial emissions, provided the使用的氢是绿色的。但是，到2050is too high to rely only on this solution。
投资也被引入新的化学过程以捕获二氧化碳而不是创建的方式制造水泥它。在所有行业中，扩展碳捕获，存储和使用（CCUS）活动可能解决20％的二氧化碳排放根据国际能源机构的说法。但是，即使在可再生能源过渡中增加了CCU，仍然没有看到我们命中零。
达到零
Tackling the emissions that remain requires a revision of how we design, make and use products and materials. In industry, there are some particularly important areas to address: chemical processes; high heat processes; and landfill and incineration. Each can be reduced by changing the way we make, use and reuse not only cement but all building materials, in ways that reduce demand for virgin resources.
仅建造和翻新建筑物11 percent of total greenhouse gas emissions in our cities，其中大部分来自水泥，钢，铝和塑料的生产。尽管碳足迹很重，half of the aluminum produced each year doesn’t even make it to a final product，而是成为废料，建筑行业已被确定为英国的第二大塑料废物生产国。During the construction process15 percent of building materials are wasted。当建筑物被拆除时，其大部分材料最终都陷入垃圾填埋场。仅在欧盟，建筑和拆除废物就会说明几乎按重量浪费的三分之一。
The drive to upgrade our buildings so that they are energy efficient and powered by renewable energy, therefore, needs to be complemented by efforts to reduce the emissions generated from making construction materials, so-called embodied emissions as well as those that come from how we deal with building materials at the end of their lives. This is where the circular economy comes into play.
三种主要的循环经济战略手机app买球靠谱吗直接解决了建筑环境的排放：
- 通过共享和重用更好地利用现有建筑物，需要创建更少的新建筑物
- 设计新的建筑物以灵活使用并消除施工中的废物
- Reusing and recycling building materials so that they don’t end up in landfill or incinerators
到2050年，这些策略总之可以将建筑和拆除建筑物的全球二氧化碳排放量减少21亿吨，使其对于达到零净至关重要。
更好地利用现有建筑物
A standard building has an expected structural and usable lifespan of 50 to 100 years, yet after less than 30 years it is often judged to lose value — its desirability and functionality — and demolition is the go-to solution, with a new building taking its place. However, if a building’s value can be maintained, and it is used more and for longer, its materials can be prevented from ending up in landfill or incinerators, and the need for new materials can be significantly reduced. Simply extending the life of existing buildings could reduce GHG emissions by 1.3 billion metric tons of CO2e per year in 2050.
One way to do this is to give old buildings a new life by adapting them as our needs change. Efforts to revitalize the harbor area in Sydney, Australia, have included adapting a1970年代的塔楼，用于重复使用，保留了68％的结构。The CO2 emissions embedded in these materials when they were made were equivalent to 10,000 airplane flights from Sydney to Melbourne.
仅仅延长现有建筑物的寿命可能会使温室气体排放量在2050年每年每年13亿吨二氧化碳。
在Covid-19-19大流行期间，有四个10 workers have switched to working from home,离开办公室和周围的零售空间空缺。为了确保使用这些建筑物而不是被拆除，已经适应了空间。2020年，特朗普政府的住房和城市发展秘书本·卡森（Ben Carson）强调the opportunity to adapt vacant office space to address housing shortages，正在开发项目。在英国，更多在2020年3月至9月之间，公司放弃了超过100万平方英尺的办公空间许多属性专门用于转换为住宅物业。这样的办公室转换也有可能限制该市外围的新住房需求，限制资源使用，相关的排放和侵占绿带地区。
While repurposing of a building may happen as infrequently as every 20 years, it equally can occur as frequently as day-to-day. Although many traditional office spaces are set for long-term conversion as a result of the pandemic,flexible coworking spaces, many of which become bars and restaurants after hours, are expected to increase in popularity。诸如此类的空间共享模型允许多个人和企业在短期内使用建筑物，改善使用和寿命，并提供可能的成本节省。在伦敦，点对点租金，更好的城市规划，办公室共享，重新利用的建筑物和多功能建筑物可能会在2036年到2036年使用20％的建筑物，每年节省超过8.49亿美元。
Designing new spaces in ways that eliminate waste
当需要竖起新建筑物时，它们可以在共享和重用时积极设计，这降低了它们变得过时或无法使用的可能性。在VíaVallejo的开发商墨西哥城已将商业，住宅和酒店空间整合到一个单一城市街区的地点，可以为不断变化的需求重新配置领域。
除了诸如此类的多用途建筑物之外，还可以像建筑师Heta所写的那样创建，“a modular and dimensionally coordinated system that will allow a space at its core to be re-made — both in terms of its bounding enclosure and internal fit out." Design informs more than just how a space is configured and used inside, it also dictates how a building is put together, what materials are needed, and whether waste is an inevitability in construction. Any waste equates to unnecessary emissions. By ensuring all materials used in the construction of buildings are entirely necessary and are used, greenhouse gas emissions can be reduced by 1.2 billion metric tons of CO2e per year.
A number of design strategies can be used to achieve these reductions. Incorporating prefabricated building elements can reduce material demand and mitigate or eliminate waste. This could reduce on-site waste generation by up to 90 percent compared to traditional construction. In Oakland, California, off-site construction of modules for a2.4英亩的中期住房开发大大减少了预期的建筑浪费。Permanent modular structures such as this also can be complemented by temporary modular structures that allow for easy relocation rather than demolition, and together these strategies have been found to offer up to 60 percent material cost savings.
Construction projects often use more materials than is actually needed due to design choices and overspecification. For example, it is often possible to achieve the same structural strength of a building using only 50 to 60 percent of the specified cement.
New technologies, such as 3D printing for foundations and supporting structures, can reduce the quantity of materials needed through innovation in structural forms, and this goes beyond buildings to other areas of the built environment. Engineering Group ARUP undertook aproject to produce 3D printed metal elementsfor a street lighting sculpture in the Netherlands, with the outcome being a structure weighing only half of the original design that used conventionally made components.
Bringing such innovations to scale would be greatly helped by reforming building regulations relating to structural safety, such as the Eurocodes in the EU. Such regulations ensure structural integrity and safety standards are maintained, but many are not designed to account for non-traditional construction methods, which allow for these standards to be met while material use is reduced. It would be valuable to review such regulations in ways that incorporate the expert input of engineers familiar with recent innovations in construction technologies and processes. Such re-evaluations also could make the use of recycled materials mandatory in new buildings and facilitate the reuse of materials in reconstruction projects.
Reusing and recycling materials
Only 20 to 30 percent of construction and demolition waste is reused or recycled. This is often due to poor design and lack of information about a building’s material composition. However, unusable or unsuitable buildings can be viewed as material banks rather than structures that must be disposed of. Careful disassembly can facilitate material reuse and recycling, which together can prevent 0.6 billion metric tons of CO2 emissions every year.
For this to happen in practice, reliable and standardized information about building components is needed. The construction industry is notoriously fragmented, with different sub-contractors often designing and developing parts of buildings without interacting with one another, which means opportunities to reuse materials are missed. However, if each component had a digital "护照" which明确定义其材料组成以及可能的重用选项，浪费材料的可能性要小得多。在阿姆斯特丹，改善2040年之前建造70,000套新公寓的材料的再利用可以减少一百万吨的浪费。
切勿拆除，切勿删除或替换，始终添加，转换和重复使用！
考虑到投资时间，金钱，能源和创造力，重复使用将材料保持在最高的价值。但是，所有材料都无法重复使用，从而使回收基础设施至关重要。使用回收而不是维珍材料将二氧化碳排放量减少40％至70％。例如，为了使钢从头开始，首先是使用爆炸炉生产液态铁。爆炸炉消耗了钢铁工厂总体能源需求的60％, so removing this process entirely by melting down steel that already has been used reduces energy demand by the same amount.
While steel recycling is well-established — with85 percent of all steel produced being recycledglobally — recycling rates for cement, plastics and other materials are much lower. To develop the market for used materials, buildings need to be designed using recyclable and recycled materials, recycling infrastructure needs to be scaled, and the quality of secondary materials assured.
Some progress is already being made. In Rotterdam, the Netherlands,15吨工业建筑废物已用于使用启动stonecycling的砖块来创建联排别墅的立面。在Denmark,再生混凝土已用于形成新仓库的元素, 80 percent of which was taken from its predecessor.
The future of our buildings
Projects to create a circular economy for the built environment are becoming increasingly ambitious. In 2019 the first手机app买球靠谱吗循环经济高架桥在荷兰开业。它可以在其他地方建造，拆卸和重建。它由40个预制混凝土块制成，旨在拥有200年的可用寿命，届时希望混凝土回收将是司空见惯的。
在Bordeaux, architects Lacaton & Vassal have made an equally powerful statement. When asked to transform the city’s public square他们的回应是“什么都不做”，或者几乎什么都没有，突出了针对再生的项目的碳足迹。他们的前景是：“永远不要拆除，切勿删除或替换，始终添加，转换和重复使用！”这是我们所有人都可以从中受益的立场。
这就是关于如何通过循环经济策略消除3.1BT温室气体排放的故事。手机app买球靠谱吗Read on to hear about the remaining 6.9BT。
