Carbon Budget

According to the new policies of the European Union, all the industries will cut their emissions by at least 55% until 2030 and become almost carbon neutral until 2050. Decarbonization is one of the most important goals of the EU and a tool to combat the climate crisis. For several years there has been a discussion on carbon outsourcing [1]

and it comes back when we want to talk about the carbon budget and a building’s carbon budget. The carbon budget is a term that connects anthropogenic GHG emission reduction with the temperature rise. It limits plans ahead, giving a maximal threshold for GHG emissions. It could be called the total carbon budget too, when referred to the sum of emission of all activities or industries. I am introducing here the term Buildings Carbon Budget (BCB), a chunk of the total carbon budget that is related to Architecture, Engineering and Construction. 

The BCB quantifies all carbon used by the industry, starting from sourcing and manufacturing, through design and construction, operation until demolition. Herewith I am going to focus on the whole life cycle of a building, which includes embodied carbon. And this is a game changer from the point of view of carbon outsourcing. It pushes the construction companies to verify products of their suppliers and manufacturers, to review their production technology, use of energy, transport and more. The BCB may seem to be very similar to the Life Cycle Assessment. And in fact it is based on the LCA, although in contrast to the LCA that assesses and measures impact to compare with other solutions, BCB estimates expenditure for a set period of time, establishes thresholds and looks for minimization of CO2 involved in the project. Similarly to cost budgeting known from economics, it could use the same repertoire of tools: incremental budgeting, budget planning, cutting, carbon flow. I will use the LCA as a starting point and therefore I need to explain it in detail. 

The method to estimate environmental impact of a building we have been following at Dosta Tec so far is described in the ISO norm 14040. It is divided in four parts [fig. 01]: (A) Production and Construction, (B) Operation, (C) End of Life, and (D) Beyond the Building. Different activities are divided into embodied impact and operation impact, and finally, materials can be divided in three groups: cradle-to-gate, cradle-to-grave, and cradle-to-cradle. Let me explain all the components and groups so that the process is as transparent as possible.

Stage A: Production and Construction, embraces all the activities needed for a building to be built. Material sourcing which could be a process that releases a big amount of CO2 if metal ores are

used and the process of getting a pure metal is carbon-expensive; large glazed (flat or curved) surfaces require not only significant amounts of fuel to be produced but also often transport from specialized glass factories. Sometimes thanks to very efficient manufacturing processes, and we are not discussing here the social aspect of that – so-called Social Life Cycle Assessment (S-LCA), in China the production carbon footprint is low, but the question of where does the material come from and how is it transported to the construction site needs to be asked. Sometimes it happens that after burdening a low-carbon product from China with high-carbon transport cost it has still lower embodied-carbon than a local product. 

Stage B is related to the operation of a building, it is related to energy and resources needed for the correct functioning of a building. For example, in commercial buildings in this stage, an important role is played by the facility manager and building integrated systems that monitor the needs of the occupants and can adjust the building’s performance according to their needs. I would like to emphasize that stages A and B are strictly related and it is highly advised that a representative of future occupants participates in the design stage. It helps the design team to make decisions based on the actual needs, and later to pass the information on the best use of the buildings to the future occupants. Today it happens more and more often with BIM 6 level.

Stage C happens when the buildings stop responding to the occupants or market needs, and cannot be reconstructed or renovated more. It is deconstruction and waste processing. This stage seems to be quite outdated since it uses the terms like a waste. Although taking into consideration that most of the buildings in Europe are 30 years or older I recognize that the ideas of circular construction were not introduced yet and many building’s components cannot be recycled or we don’t know how to recycle them.

Finally, Stage D is related to a building afterlife. All the parts of the building are looking for use in another building or to be recycled. Here the topic of Building as Material Banks appears. At all the stages we can set up a yearly or total carbon budget as we set a financial budget. All the activities’ emissions can be measured across their lifecycle. The stages can also be thought of in three groups: cradle-to-gate,  cradle-to-grave, and cradle-to-cradle. The first assesses only the sourcing and production process (i.e. half of Stage A), it is the most common in Environmental Product Declarations (EPD) and is a good tool to compare how the product is manufactured but does not measure the afterlife of the product. If a product is biodegradable it is a great attitude. But typically it gives a false impression while comparing insulation materials such as hemp fibre and XPS. In the cradle-to-gate approach, they might have the same environmental impact, or maybe even XPS has a lower environmental impact, but it does not assess the impact after the afterlife of the product. How many resources are needed to process it or decompose it? Cradle-to-grave (i.e. Stages A to C) assesses the impact of a material that would be processed and disposed of, it means that it will not become a part or raw material for the next cycle of the material nor nutrient. Finally, cradle-to-cradle (i.e. all four stages) defines all the materials that would stay in a closed loop of use. There is no need for sourcing after recovery and recycling. Although it does not mean that there is no carbon footprint in manufacturing or sourcing. It is also important to verify where it is recycled and recovered. Unfortunately, at the present time, the information is not transparent and confirmed yet.

The Buildings Carbon Budget is a measure that helps to meet with the decarbonization of the industry. No doubt it is a difficult task. It is about planning, measuring and integrating all the parties involved in the building lifecycle. Making it a sum of all the activities engages everyone and at the same time helps to avoid a situation when carbon is being outsourced to another stage of a building. By making it a total measure we ensure that every stage and all the parties involved are compromised to stay within carbon limits. The first challenge is to establish actual thresholds for build typologies and locations. In Dosta Tec we are building our internal database when simulating building performance, and embodied energy and carbon to be able to establish a carbon budget for our next projects.

Adrian Krężlik

[1] It is an effect of moving factories and production from Europe to Asia and other places. Companies and factories located in Europe are obliged to meet certain standards, including CO2 emission. Their subcontractors, producing parts, are often located in areas where standards are not high. 

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