Greenhouse Gas Emissions from Excavation on Residential Construction Sites

Perry Forsythe,Grace Ding

doi:10.5130/ajceb.v14i4.4195

Abstract

Despite considerable research concerning the manifestation of greenhouse gases in the usage of buildings, little has been done concerning emissions arising from the construction process itself. This paper specifically examines emissions arising from cut and fill excavation on residential construction sites. Even though such excavation is often seen as being economical in terms of providing a flat base for concrete raft slab construction, the environmental consequences of this approach need to be considered more fully in terms of impact on the environment. This is particularly important when steeply sloping sites are involved and for different soil types. The paper undertakes a study that quantitatively assesses the cumulative greenhouse gas emissions caused by cut and fill excavation on 52 residential projects in Australia for a range of slope and soil types. The paper presents results from the study and concludes that greenhouse gas emissions increase as site slope increases; the building footprint area (as distinct from Gross Floor Area), exposes the need to reduce the area of the building to reduce greenhouse gas emissions; excavation of rock soils creates higher emissions than other soil types; and cut and fill excavation on steeply slope sites increase emissions. Potential alternative construction includes suspended floor construction systems which involve less excavation.

Highlights

The building construction process is well known as a source of excessive resource consumption, pollution and a threat to biodiversity (Dimoudi & Tompa 2008)
The results indicate that slope has a positive correlation with cumulative greenhouse gas (GHG) emissions
The study analysed GHG emissions under two distinct scenarios including the rate of emissions relative to Building Footprint (BF) area, and relative to Gross Floor Area (GFA), for each dwelling The results indicate that the former is in many ways the most appropriate performance measure of the two because it more directly exposes the need to reduce cumulative GHGs emissions associated with construction on sloping sites by minimising the part of the dwelling in touch with the ground

Summary

Introduction

The building construction process is well known as a source of excessive resource consumption, pollution and a threat to biodiversity (Dimoudi & Tompa 2008). CO2 is adopted as a reference point to convert different gases into CO2 equivalence (CO2-e) In this context, Yan et al (2010) define four sources of GHG emissions relating to building construction including: the manufacture and transportation of building materials; energy consumption of construction equipment; energy consumption for processing resources; and disposal of construction waste. These have been taken into account in the current research but key issues of note include the impact of equipment on excavation processes and the removal of any spoil taken off site. The soil classification used in the study reflected the same classification system as used in Australian Standard AS2870 being the Residential Slab and Footings Code (SAI Global 2011)

Site 2 Sites 3 Sites 6 Sites 12 Sites

Findings

Conclusion