Evaluation of the Carbon Reduction Potential of the EU Residential Building Stock based on Sustainable Land Area Requirements

Abstract

The use of biomass as a construction material is a great way to store atmospheric carbon and to decrease the construction industry’s carbon footprint. Carbon is temporary stored in the building stock for the duration of the buildings’ lifetime. Employed on a large scale, this can alter atmospheric carbon dynamics and help reducing the greenhouse gas emissions causing climate change. Massive biomass deployment however requires great cultivation areas which can lead to unwanted land use change. While land use change has been intensely studied, the impact of a heavy use of biomass for construction has not.

The aim of this thesis is to determine how much biomass and thus cultivation area of what plant would be needed to meet the material requirement of expected new construction (by 2050) and retrofitting the existing residential building stock to fulfill the current thermal insulation requirements in the European Union as it is today (EU-28). Based on the present land use, the resource potential for different biogenic materials is determined, which then serves to appoint the share of the EU’s residential building stock that can be retrofitted/built with what kind of biomass without causing unsustainable land use change.

This work splits reality into four systems: the built environment and the natural environment are the main systems. They are connected through the production system which transforms raw biogenic material into ready-to-use construction material. Further there is the Carbon Balance system which models production and construction emissions and carbon uptake through plant growth. The built environment comprises the input data (e.g. Tabula data base, population growth forecasts etc.), the residential building stock model, new construction model, technology options, construction material requirement model. The natural environment entails the raw material requirement model and the land use model on the demand side and data on biomass cultivation and production (e.g. EuroStat) on the supply side. The comparison of the existing cultivation area with the demanded land detects possible land scarcities depending on the raw materials examined. Statements about resource scarcity and abundancy can be made and thus the material-based practicability of the different technology options can be determined.

Finally a traditional LCA (cradle-to-gate) is conducted, obtaining the gross CO2,eq emissions in order to derive the net CO2,eq emissions, to check for net carbon storage. Cultivation and harvesting of the biomass as well as raw material processing and production lie within the LCA boundaries. Demolition and end of life of the buildings as well as by-product treatment are not considered in this work.

An effective carbon storage potential of 442 Mt CO2,eq was found for the timber-based technology option. The straw-based technology option showed a carbon storage potential of 394 Mt CO2,eq. Effective carbon storage from deploying hemp- and cork-based technology options was found to be irrelevant, since not enough cultivation land was available.