With a major focus on the effects of global warming and co-ordinated efforts across the world underway to help reverse climate change, the building industry regularly comes under scrutiny.
After all, according to the United Nations Environmental Programme, buildings and their construction account for 36% of global energy use and 39% of energy-related carbon dioxide emissions annually.
Carbon capture is one way which is gaining more attention as the building industry seeks to comply with new regulations and goals relating to carbon emissions.
What is carbon capture technology?
Carbon capture and sequestration/storage (“CCS”) is the process of capturing carbon dioxide (CO₂) formed during power generation and industrial processes, and storing it so that it is not emitted into the atmosphere.
It is believed that CCS technologies have significant potential to reduce CO₂ emissions in energy systems as they can capture up to 90% of CO2 released by burning fossil fuels in electricity generation and processes such as cement production. Furthermore, some building materials actually absorb carbon so that it is not emitted into the air.
How do homes and developments contribute to the carbon crisis with specific detail around the main contributors?
Burning fossil fuels, changing land use, and using limestone to make concrete all emit significant quantities of carbon into the atmosphere.
Such emissions are a combination of two things. First is day-to-day energy use—known as the “operational carbon emissions” that comes from providing power for lighting, heating, and cooling and accounting for about 28% on a global basis annually.
Second is the “embodied carbon” of a building which is the amount of carbon generated through manufacturing building materials, transporting materials to construction sites, and the actual construction process. This accounts for about 25% of a building’s total lifecycle carbon emissions or 11% on a global basis.
Ways in which the building sector can reducing carbon emissions
Decarbonisation, or trying to eliminate carbon dioxide emissions, in the building industry can be undertaken in several ways.
The first way is by reducing consumption through energy efficient design as most building-related carbon emissions come from energy use. The second is replacing fossil fuels with alternative carbon-free renewable energy.
To achieve a net-zero carbon building, including embodied carbon, will mean that the building has to produce enough renewable energy to meet operations annually and offset the carbon emitted from construction.
The architectural and building industry continue to explore ways they can make a difference—work that has been going on for many years through certification programmes such as LEED or the Living Building Challenge. But with the 2050 deadline for zero-carbon buildings under the Paris Agreement now less than 30 years away, time is becoming of the essence.
What materials or technologies can be used within a development to capture carbon from the air?
There are a number of materials and technologies already in use aiming at mitigating the effects of carbon emissions during the construction cycle, including plant matter such as cork or hemp.
There is also algae which captures atmospheric carbon via photosynthesis and using it directly and, of course, the ubiquitous wood. As an example, it is estimated that a fully-grown tree can remove 22kg of CO2 from the atmosphere over the course of a year.
Some of the newer materials being developed include:
Mycelium insulation which is derived from a bio-material that forms the root system of fungi, feeds on agricultural waste and in the process sequesters the carbon that was stored in this biomass.
Companies such as London-based Biohm are using mycelium to create building insulation that is naturally fire-retardant and is said to remove at least 16 tonnes of carbon per month from the atmosphere as it grows.
Bioplastic is a carbon-negative bioplastic made in Germany which can be used in cars, interiors and cladding. The material contains biochar, a carbon-rich substance made by burning biomass without oxygen, which prevents the carbon from escaping as CO2.
Bio-based hybrid foam, infused with a high number of CO2-adsorbing ‘zeolites’ -microporous aluminosilicates. The porous, open structure of the material gives it a great ability to absorb carbon dioxide.
Carpet tiles made almost exclusively from recycled plastic and various biomaterials, which the manufacturer Interface says store more embodied carbon than is emitted by the products in their production. They aim to make its entire product range carbon negative by 2040.
Other materials in use include olivine sand, 3D printed wood, ad concrete blocks (carbicrete), bricks, food and even vodka.
Some major technologies being developed for carbon capture at the source of emission
Such technologies fall into three categories: post-combustion carbon capture (used in existing power plants), pre-combustion carbon capture (mainly used in industrial processes), and oxy-fuel combustion systems.
Examples are:
Oxy-fuel combustion is the process of burning a fuel using pure oxygen, or a mixture of oxygen and fuel gas, instead of air. Previously, the primary use of oxy-fuel combustion was in welding and the cutting of metals, especially steel, since oxy-fuel allows for higher flame temperatures than can be achieved with an air-fuel flame.
Over recent years the process has received a lot of attention as a potential carbon capture and storage technology.
Absorption is a condition in which something takes in another substance and, hence, carbon can be absorbed. It is a chemical process in which atoms, molecules or ions become either solid or liquid material. This is a different process from adsorption as molecules undergoing absorption are taken up by the volume, not by the surface as in the case for adsorption. The term sorption covers absorption, adsorption and ion exchange.
Membranes/membrane cartridges: gas mixtures can be separated by synthetic membranes made from polymers such as polyamide or cellulose acetate or from ceramic materials but have some limits on performance.
Owing to this and cost issues, membrane materials have expanded into the realm of silica, zeolites, metal-organic frameworks and perovskites due to their strong thermal and chemical resistance as well as their ability to be modified leading to increased permeability and selectivity.
Other new technologies include:
- multi-phase absorption;
- adsorption;
- chemical looping combustion;
- calcium looping; and
- cryogenic.
CCS project underway globally
North America has the largest number of CCS projects with 16 of the 22 operational or under construction.
Of the 22 active global projects three are power stations; nine industrial facilities manufacturing iron or processing tar sands and ten projects at natural gas processing facilities.
There are five planned CCS projects in the UK, but none has reached the construction phase. Despite a government pledge of £1 billion in funding, progress to embrace such technology has been slow.
Final thoughts
Given that it is one of the main contributors to the carbon crisis, the construction and development industry must be held more accountable for the reversal or the capture of CO2 emissions it creates.
With better use of established materials such as wood or cork and new materials coming to market which are eco-friendly, now is the time for industry players and governments to get their strategy right. New technologies will, of course, also help but it needs a co-ordinated effort from all concerned parties to try to reach net-zero and make sure CCS really delivers and helps in the fight to reverse climate change.
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