The climate crisis caused by carbon emissions
since the beginning of the industrial revolution in the mid-19th century, human activities have added more carbon dioxide and other heat-absorbing gases to the atmosphere, thereby disturbing natural processes to reach equilibrium and greatly contributing to climate change. With rapid industrialization, population increase, urbanization density and significant changes in lifestyles, the burning of coal, oil and natural gas has emitted about 500 billion tons of carbon dioxide, about half of which remains in the atmosphere. The impact of these additional carbon dioxide emissions in the atmosphere contributes to the rise in global temperatures and greenhouse gas levels, leading to man-made global warming effects.
The concentration of carbon dioxide in the atmosphere continued to grow to about 390 ppm or 39 percent above pre-industrial levels in 2010, with global average temperatures rising between 1850 and 1899 and between 2001 and 2005. 0.76°C.
II. Energy Saving and Carbon Reduction
based on the threats of greenhouse gas emissions, it is urgent to curb the development of the greenhouse effect. In this context, december 12, 2015 nearly 200 parties to the "United Nations Framework Convention on Climate Change" unanimously agreed to adopt the "Paris Agreement" at the Paris Climate Change Conference to make arrangements for the global response to climate change after 2020.
The agreement pointed out that all parties will strengthen the global response to the threat of climate change, control the global average temperature rise within 2 degrees Celsius from the pre-industrial level, and work hard to control the temperature rise within 1.5 degrees Celsius. The world will achieve the peak of greenhouse gas emissions as soon as possible, and achieve net zero greenhouse gas emissions in the second half of this century.
An overview of the world's carbon emissions, the total global emissions in 2020 are about 32 billion tons. Among them, China is about 10 billion tons, accounting for 31%. Although my country's per capita carbon emission level is less than 50% of that of the United States, factors such as a large population, a large manufacturing country, and a large import and export country have already shaped China into the world's largest carbon emission country.
Under this premise, China resolutely became the first batch of countries to sign the Paris Agreement and took the initiative to assume the responsibility of taking off and landing carbon. In the national independent contribution document submitted by China before the Paris Conference, it proposed to peak carbon dioxide emissions around 2030 and strive to achieve it as soon as possible. In 2030, carbon dioxide emissions per unit of GDP will drop by 60% to 65% compared with 2005, and the proportion of non-fossil energy in primary energy consumption will reach 20% about 4.5 billion cubic meters of forest stock increased from 2005.
On October 24, 2021, the Central Committee of the Communist Party of China and the State Council issued the "Opinions on the Complete, Accurate and Comprehensive Implementation of the New Development Concept to Do a Good Job in Carbon Peak and Carbon Neutralization" ("Opinions"), as the "1" in the "N" policy system, the "Opinions" carried out systematic planning and overall deployment for the major work of carbon peak and carbon neutralization. Presented in Release five main objectives: Building a green and low-carbon circular development economy; improving energy efficiency; increasing the proportion of non-fossil energy consumption; reducing carbon dioxide emissions; improving the carbon sink capacity of the ecosystem.
Then on October 26, the State Council issued the "Carbon Peak Action Plan by 2030". According to the plan, by 2025, the proportion of non fossil energy consumption will reach about 20%, the energy consumption per unit of GDP will be reduced by 13.5 compared with 2020, and the carbon dioxide emission per unit of GDP will be reduced by 18% compared with 2020, laying a solid foundation for the realization of carbon peak. By 2030, the proportion of non-fossil energy consumption will reach about 25% carbon dioxide emissions per unit of GDP decreased by more than 65% compared with 2005, successfully achieving the carbon peak by 2030 and the carbon neutral target by 2060.
III. The "contribution" of buildings to carbon emissions"
as we all know, world energy consumption is divided into three main economic sectors: construction, transportation, industry.
In these three areas, buildings, including residential, commercial, light commercial and institutional, account for about 1/3 of total energy consumption compared with other energy-using sectors. Fossil energy consumption is the main source of carbon emissions.
According to the World Energy Agency (IEA), buildings account for 30-40% of total greenhouse gas emissions(Figure 4), construction-related greenhouse gas emissions reached 12.5 billion metric tons (t) CO2 equivalent (e). Since the 1950 s, construction sector greenhouse gas emissions have been steadily rising. Over the next 25 years, these emissions are expected to grow faster than any other economic sector.
Carbon emissions from the construction sector come from the greenhouse gases produced during the production and transportation, construction and demolition, and operation phases of the building materials associated with the building. According to the "China Building Energy Consumption Research Report (2020)", the total carbon emissions from the whole construction process in the country account for more than half of the total carbon emissions in the country, of which building materials (steel, cement, aluminum, etc.) account for 28%; The operation phase (urban residential construction, public buildings, rural buildings) accounted for 22%, and the construction phase accounted for 1%.
This trend in building energy consumption is influenced by several key factors. These factors include population growth, urban density, spatial organization, economic growth, building size, building operations, building longevity, occupant behavior, geographic location, climatic conditions, and service needs.
In terms of the percentage of building energy consumption, the services required by buildings in heating, ventilation and air conditioning (HVAC) systems account for a large part of building energy consumption, exceeding 60% of the total building energy consumption. At the same time, lighting accounts for about 11 - 20% of a building's total energy demand. According to the IEA report, in China, air conditioning and heating systems account for 65% of the total energy consumption of buildings. In addition, the building energy consumption due to ventilation and infiltration accounts for about 30 - 50% of the total energy consumption. Since about 70% of the electricity comes from thermal power, the carbon emissions caused by energy consumption can be seen.
Worldwide Green Building Evaluation Standards Help Carbon Neutrality
how to standardize and quantify building carbon emission control has become a new topic.
One of the best ways to get new projects started on the right low carbon footing is to follow the guidelines set by these standards.
There are many different rating systems that provide standards for green building design. There are not only China's green building evaluation standards, but also LEED, BREEAM, DGNB and other international standards. The definition of green building itself is a high-quality building that saves resources, protects the environment, reduces pollution, provides people with healthy, applicable and efficient use of space, and maximizes the realization of harmonious coexistence between man and nature in the whole life cycle. To varying degrees, it can provide auxiliary effects for the mitigation of building carbon emissions.
Evaluation Standard of Green Building in China
china's green building certification is a national evaluation standard issued by the Ministry of Housing and Urban-Rural Development. The certification is based on the current situation of my country's buildings and is evaluated from multiple dimensions such as safety, health, convenience, and energy saving. It is currently used in China. The most extensive green building certification system.
For CO2 emissions, the standard has a series of scoring measures, multi-dimensional carbon reduction:
a. Safety and durability: the standard stipulates the durability and weather resistance of buildings and the degree of spatial flexibility. It is hoped that the frequency of major building demolitions and major changes can be reduced by constructing highly adaptable building buildings, and the life cycle of the building can be prolonged as much as possible, thereby reducing the possibility of additional carbon emissions from the building.
B. Energy efficiency: the energy efficiency of building HVAC systems, lighting systems and the use of energy saving strategies are clearly defined. Minimize building energy consumption.
c. The surrounding environment of the building: in the standard, there are multi-dimensional scoring criteria for public transportation and infrastructure facilities around the building land, hoping to reduce indirect carbon emissions caused by transportation.
d. Renewable energy: encourage the use of renewable energy and reduce the proportion of electricity used in the grid.
e. Calculation and analysis of building carbon emissions: as a bonus item, the score is relatively high, but the index control is relatively mild, which has a good role in promoting the popularity of carbon emission calculation in China's construction industry.
2. LEED
LEED is the "Green Building Assessment System" (Leadership in Energy & EnvironmentalDesign Building Rating System) established and implemented by the American Green Building Association. It is referred to as LEED in the international community. It is currently considered as one of the various building environmental assessment, green building assessment and building sustainability assessment standards in various countries around the world. The most perfect and influential and the most widely commercialized assessment criteria. LEED's vision for the built environment includes three strategies: reducing implied carbon; protecting human and ecological health; and developing a circular economy. Reducing implied carbon is a key consideration for buildings and spaces in standard evaluations.
The contents of the standard evaluation clauses that can help reduce the carbon emissions of buildings include:
use less energy and water: there is an opportunity to reduce the consumption of fossil fuels and electricity when buildings improve their water utilization by conserving water, recycling water, etc. Similarly, LEED encourages water resources to be used to produce, transport and treat water, thereby reducing the "hidden carbon" of buildings ".
B. Consider life cycle impacts: LEED encourages a life cycle assessment of building materials and products, and in turn a life cycle assessment of the entire building. Life cycle analysis in the form of whole building life cycle assessment and environmental product declaration; material composition reporting and optimization; responsible for raw material procurement; and waste reduction and management. These scoring points are distributed across multiple scales throughout the building life cycle to achieve the goal of actually reducing carbon emissions.
c. Support for sustainable strategies: green buildings provide mechanisms to positively impact residents in ways that support the climate. For example, buildings can create opportunities for more composting and less landfill, as well as opportunities for alternative transportation.
d. Green sites and traffic: LEED also has a score on the siting of building sites, encouraging links to transportation and amenities, as well as preserving and creating natural vegetation areas and rooftops, potentially reducing carbon emissions from commuting or transportation during future operations.
e. Renewable energy options: LEED endorses buildings using various contractual mechanisms for off-site procurement of renewable energy. Establishing a LEED standard that addresses the age of renewable energy generation buildings helps guide project teams' decisions and direct investments to increase renewable energy supply on the grid.
f. Transportation energy use: the location and transportation chapter requires new buildings to improve land use patterns and allow building users to use public transportation, which helps reduce greenhouse gas emissions from motor vehicles.
3. BREEAM
the British Building Research Institute Environmental Assessment Method (English name: BREEAM-Building Research Establishment Environmental Assessment Method) is called the British Building Research Institute Green Building Assessment System. BREEAM was founded in 1990. The world's first it is also one of the most widely used green building assessment methods in the world.
As the earliest the green building system, BREEAM has long proposed the importance of carbon emissions, not only targeted to reduce carbon emissions score items, but also other related score items to assist in the realization of this goal:
a. Low carbon design: the expected carbon emissions of the building must be reported on the basis of meeting local building codes. Especially with regard to the energy needs of buildings for heating and cooling, as well as direct and indirect carbon emissions.
B. Building Life Cycle Assessment (LCA): the implied carbon of building materials is also one of the key concerns. In the material chapter 01, the building is required to carry out life cycle analysis and evaluation. The purpose of the assessment is to consider the possible impact of sustainability, maintenance and replacement cycles of carbon and materials.
c. Building digital monitoring: the standard monitors and manages building energy consumption and building water consumption during operation. Make full use of energy and water resources without leakage, reduce unnecessary waste of resources, and ensure that the building operates according to the expected value of the design, so as to avoid carbon emissions above the estimated value.
d. Waste Disposal: the assessment of the management of waste generated during the construction, use and demolition phases of a building is also an important part of the BREEAM standard. The unreasonable disposal of waste will generate additional carbon emissions in the life cycle of the building.
e. Green Transportation: BREEAM has an entire chapter on transportation, which aims to reduce carbon emissions from transportation as much as possible under the prerequisite of comfort and convenience for building users. Such as access to public transport, the convenience of infrastructure, other alternative modes of transport.
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