Seppo Junnila

Urban planners’ control over earthworks can result in remarkable greenhouse gas reduction

Urban planners are in a unique position to steer and regulate urban regeneration. Given the massive material flows of new construction, it seems evident that the environmental objectives of urban planning should target the immediate development phase as well as the future use phase of the built environment. Nevertheless, the potential of urban planning to contribute to mitigation of climate change is often only considered to lie in the use phase. Densification, improved public transportation infrastructure and new energy efficient buildings are seen to be the core elements of sustainable urban development. However, the gains attributed to reductions in transport and housing emissions contribute to climate change mitigation only after the demerits of new construction are redeemed.Within the current time frame of climate change mitigation targets, the negative effect of the immediate emissions from construction becomes extremely relevant. Multiple studies have stressed the rising importance of the construction phase in a building’s or residential area’s life cycle GHG emissions. In addition to emissions from aboveground construction, earthworks account for a considerable amount of GHG emissions. In Finland, the yearly consumption of natural mineral aggregates is approximately 100 million tonnes, and local depletion of materials gradually lengthens the transport distances. Surpluses of soil and blasted rocks are more often seen as being troublesome to discard as opposed to being useful resource. The purpose of this study was to investigate if reducing the GHG emissions of earthworks could be a relevant part of sustainable urban planning.A single case study was conducted to assess the magnitude of GHG reduction that can be achieved by an urban planner’s control over earthworks. The case area was a 120 hectare wide residential development for 5,000 inhabitants, located in the Northwest corner of Helsinki, the capital of Finland. The case study covered three planning solutions that intended to reduce the transportation of rock and soil materials: (1) local use of blasted stone, (2) a hill made of surplus clay, and (3) minimal refurbishment of a pond. The three planning solutions reduced the GHG emissions of earthworks by 2,360 tonnes. In addition, particle emissions were reduced by 420 kg. The immediate GHG emissions savings were equivalent to 250 inhabitants giving up use of private vehicles for 10 years.

Carbon footprint and rebound of large scale building integrated energy production

Building integrated renewable energy production, such as solar energy solutions, reduce the greenhouse gas emissions (GHG) caused by operational energy consumption of buildings. What is less understood, however, is how the investment in these sort of energy solutions affects the overall GHG emissions caused by the person or the company that makes the investment.In general, all economic activities cause environmental impacts. Thus, it has been suggested that the boundaries of environmental assessments should not be based on physical boundaries, but rather monetary budgets. For example, carbon footprints of consumers have revealed that investments in energy efficiency do not only reduce the GHG emissions caused by energy consumption, but also the emissions caused by consumption of other goods and services. This is due to the reality that consumers must withdraw the funds for the investment from some other purposes. However, when the investment in energy efficiency starts to make profit, the situation is reversed. The money saved from declining energy consumption is used on goods and services, which again increases the GHG emissions. The phenomenon is called the environmental rebound effect. The rebound effect caused by an investment is usually negative, meaning additional GHG reductions. The rebound effect caused by (energy) savings is usually positive, meaning additional GHG emissions prompted by the new consumption enabled by the savings.The purpose of this study is to assess the carbon footprint, and demonstrate the rebound effects over time, caused by investments in large scale building integrated solar energy production. The study takes into account the embodied GHG emissions in the new energy system. The rebound effects are estimated with various assumptions about the alternative consumption or investment. The study highlights why the monetary and time dimensions are important, when considering the overall environmental impacts of green investments.