Studying the demand-side vis-à-vis the supply-side of urban water systems – case study of Oslo, Norway

<div><p>The research focus of resource consumption and emissions from urban water services has, by and large, been restricted to what comes under the domain of the urban water utilities – the upstream sub-systems of water treatment and supply and the downstream sub-systems of wastewater collection, treatment and disposal. However, the material and energy flows necessitated by activities in the water demand sub-system (households, for instance) are by no means negligible. This paper studies the per-capita material and energy requirements, and the related emissions and life cycle environmental impacts, associated with water consumption in households of the city of Oslo for the year 2009. For example, the per-capita energy consumption in the household consumption phase, at 1.38 MWh per year, is eight times more than the corresponding consumption for the entire water-wastewater utility. All findings, taken together, clearly demonstrate the imperativeness of paying more attention to the demand-side management issues.</p></div

Comparative emission analysis of low-energy and zero-emission buildings

<p>Different designs and concepts of low-energy and zero-emission buildings (ZEBs) are being introduced into the Norwegian market. This study analyses and compares the life cycle emissions of CO₂ equivalents (CO₂e) from eight different single-family houses in the Oslo climate. Included are four ZEBs: one active house, two passive houses, and a reference house (Norwegian building code of 2010). Monthly differences in CO₂e emissions are calculated for the seasonally sensitive Norwegian context for electricity generation and consumption. This is used to supplant the previous applied symmetric weighting approach for CO₂e/kWh factors for import and export of electricity for the ZEB cases. All the ZEBs have lower use-stage emissions compared with the other buildings or the reference case. Embodied impacts are found to be 60–75% for the analysed ZEB cases, confirming the importance of embodied impacts in Norwegian ZEBs. The lowest total emissions were from the smallest ZEB, emphasizing area efficiency. The highest emissions were from the reference case. By abandoning the symmetric approach, a new perspective was developed for assessing the performance of ZEBs within the Norwegian context. One of four ZEB cases managed to balance out its annual energy-related emissions.</p

Assessment of Food Waste Prevention and Recycling Strategies Using a Multilayer Systems Approach

Food waste (FW) generates large upstream and downstream emissions to the environment and unnecessarily consumes natural resources, potentially affecting future food security. The ecological impacts of FW can be addressed by the upstream strategies of FW prevention or by downstream strategies of FW recycling, including energy and nutrient recovery. While FW recycling is often prioritized in practice, the ecological implications of the two strategies remain poorly understood from a quantitative systems perspective. Here, we develop a multilayer systems framework and scenarios to quantify the implications of food waste strategies on national biomass, energy, and phosphorus (P) cycles, using Norway as a case study. We found that (i) avoidable food waste in Norway accounts for 17% of sold food; (ii) 10% of the avoidable food waste occurs at the consumption stage, while industry and retailers account for only 7%; (iii) the theoretical potential for systems-wide net process energy savings is 16% for FW prevention and 8% for FW recycling; (iv) the theoretical potential for systems-wide P savings is 21% for FW prevention and 9% for FW recycling; (v) while FW recycling results in exclusively domestic nutrient and energy savings, FW prevention leads to domestic and international savings due to large food imports; (vi) most effective is a combination of prevention and recycling, however, FW prevention reduces the potential for FW recycling and therefore needs to be prioritized to avoid potential overcapacities for FW recycling

Carbon Emissions of Infrastructure Development

Identifying strategies for reconciling human development and climate change mitigation requires an adequate understanding of how infrastructures contribute to well-being and greenhouse gas emissions. While direct emissions from infrastructure use are well-known, information about indirect emissions from their construction is highly fragmented. Here, we estimated the carbon footprint of the existing global infrastructure stock in 2008, assuming current technologies, to be 122 (−20/+15) Gt CO₂. The average per-capita carbon footprint of infrastructures in industrialized countries (53 (±6) t CO₂) was approximately 5 times larger that that of developing countries (10 (±1) t CO₂). A globalization of Western infrastructure stocks using current technologies would cause approximately 350 Gt CO₂ from materials production, which corresponds to about 35–60% of the remaining carbon budget available until 2050 if the average temperature increase is to be limited to 2 °C, and could thus compromise the 2 °C target. A promising but poorly explored mitigation option is to build new settlements using less emissions-intensive materials, for example by urban design; however, this strategy is constrained by a lack of bottom-up data on material stocks in infrastructures. Infrastructure development must be considered in post-Kyoto climate change agreements if developing countries are to participate on a fair basis