Currently Asst. Prof. at Leiden University. Formerly MSCA-IF fellow at TU Berlin, PhD at Yale School of the Environment

Publications

An up to date list of all publications can be found on my Google Scholar

Comparing urban form influences on travel distance, car ownership, and mode choice (2024) Transportation Research Part D, with Florian Nachtigall, Aneeque Javaid, Nikola Milojevic-Dupont, Felix Wagner & Felix Creutzig

Paper (open access) Permanent repository tweet github

Abstract

Steady growth in global greenhouse gas emissions from transport is driven by growing demand for car travel. A sizable body of research investigates influences of urban form on travel behavior, but few European studies illustrate variation of these influences across multiple cities and countries using disaggregated data. Here, we compare car ownership and mobility patterns, and we use gradient boosting decision tree and regression models to investigate urban form influences on travel distances, vehicle ownership, and mode choice across nineteen diverse European cities. Residential proximity to the city center is the urban form feature with greatest predictive importance for trip distances, car ownership and car mode choice. The exponential reduction of car use with higher population density is clearly demonstrated with aggregate city data. We detect nonlinear relationships between urban form and modelled outcomes, identify urban form thresholds for sustainable mobility, and suggest targeted policy interventions.

Decarbonization pathways for the residential sector in the United States, 2020-2060 (2022) Nature Climate Change, with Eric J.H. Wilson, Janet L. Reyna, Anthony D. Fontanini & Edgar G. Hertwich

Paper Accepted Manuscript Blog Post News tweet github

Abstract

Residential GHG emissions in the United States are driven in part by a housing stock where onsite fossil combustion is common, home sizes are large by international standards, energy efficiency potential is large and electricity generation in many regions is GHG intensive. In this analysis, we assess decarbonization pathways for the US residential sector to 2060, through 108 scenarios describing housing stock evolution, new housing characteristics, renovation levels and clean electricity. The lowest emission pathways involve very rapid decarbonization of electricity supply alongside extensive renovations to existing homes, including improving thermal envelopes and heat pump electrification of heating. Reducing the size and increasing the electrification of new homes provide further emission cuts and combining all strategies enables reductions of 91% between 2020 and 2050. The potential of individual mitigation strategies shows great regional variation. Reaching zero emissions will require simultaneous deployment of multiple strategies and greater reduction of embodied emissions.

Material flows and GHG emissions from housing stock evolution in US counties,2020-2060 (2021) Buildings & Cities, with Edgar G. Hertwich

Paper (open access) tweet1 tweet2 github YouTube

Abstract

The evolution of housing stocks determines demand for construction materials and energy, and associated emissions of greenhouse gasses (GHGs). The contribution of construction to building life-cycle emissions is growing as buildings become more energy efficient and the energy supply decarbonizes. A housing stock model is developed for counties in the United States using dynamic vacancy rates which endogenously influence stock out- and inflows. Stocks of three house types and 10 construction cohorts are projected for all contiguous US counties for the period 2020–60. Inflows and outflows of construction materials are then estimated along with GHG emissions associated with material production and construction activities in scenarios defined by stock turnover rates, population share by house type, and floor area characteristics of new houses. The results provide new insights into the drivers of construction-related emissions at local and national levels, and identify opportunities for their reduction. Demolition material flows grow in relation to construction material flows over the analysis period. Increasing the stock turnover rate increases future floor area per person, material requirements, and emissions from construction. Scenarios with reduced floor area and more multifamily homes in new construction have lower floor area growth, material requirements, and emissions from construction.

Policy relevance

Housing construction constitutes an important share of annual residential GHG emissions in the US. The characteristics of new construction also influence residential energy use over longer time periods. Increasing the share of multifamily housing in construction and reducing the average size of new single-family homes by eliminating very large homes are two strategies that can reliably and substantially reduce the environmental burdens of new construction. These same strategies would limit or, if combined, reverse the growth of residential floor area per person, enabling reductions of energy-related emissions. Policymakers can therefore reduce residential sector emissions in the short and long terms by encouraging the supply of multifamily homes and smaller housing typologies, and limiting construction of large homes.

Drivers of change in U.S. residential energy consumption and greenhouse gas emissions, 1990-2015 (2021) Environmental Research Letters with Kenneth T. Gillingham & Edgar G. Hertwich

Paper (open access) News1 News2 tweet github

Abstract

Annual greenhouse gas (GHG) emissions from residential energy use in the United States peaked in 2005 at 1.26 Gt CO2-eq/yr, and have since decreased at an average annual rate of 2% yr−1 to 0.96 Gt CO2-eq/yr in 2019. In this article we decompose changes in US residential energy supply and GHG emissions over the period 1990–2015 into relevant drivers for four end-use categories. The chosen drivers encompass changing demographics, housing characteristics, energy end-use intensities, and generation efficiency and GHG intensity of electricity. Reductions in household size, growth in heated floor area per house, and increased access to space cooling are the main drivers of increases in energy and GHG emissions after population growth. Growing shares of newer homes, and reductions in intensity of energy use per capita, household, or floor area have produced moderate primary energy and GHG emission reductions, but improved generation efficiency and decarbonization of electricity supply have brought about far bigger primary energy and GHG emission reductions. Continued decline of residential emissions from electrification of residential energy and decarbonization of electricity supply can be expected, but not fast enough to limit climate change to 1.5 °C warming. US residential final energy demand will therefore need to decline in absolute terms to meet such a target. However, without changes in the age distribution, type mix, or average size of housing, improvements in energy efficiency are unlikely to outweigh growth in the number of households from population growth and further household size reductions.

Linking Housing Policy, Housing Typology, and Residential Energy Demand in the United States (2021) Environmental Science & Technology with Kenneth T. Gillingham & Edgar G. Hertwich

Paper (open access) News Award (EST best paper runner up) tweet github

Abstract

Residential energy demand can be greatly influenced by the types of housing structures that households live in, but few studies have assessed changes in the composition of housing stocks as a strategy for reducing residential energy demand or greenhouse gas (GHG) emissions. In this paper we examine the effects of three sequenced federal policies on the share of new housing construction by type in the U.S., and estimate the cumulative influence of those policies on the composition of the 2015 housing stock. In a counterfactual 2015 housing stock without the policy effects, 14 million housing units exist as multifamily rather than single-family, equal to 14.1% of urban housing. Accompanied by floor area reductions of 0–50%, the switch from single- to multifamily housing reduces energy demand by 27–47% per household, and total urban residential energy by 4.6–8.3%. This paper is the first to link federal policies to housing outcomes by type and estimate associated effects on residential energy and GHG emissions. Removing policy barriers and disincentives to multifamily housing can unlock a large potential for reducing residential energy demand and GHG emissions in the coming decades.

Capital in the American carbon, energy, and material footprint (2020) Journal of Industrial Ecology with T. Reed Miller, Yasushi Kondo & Edgar G. Hertwich

Paper News Spreadsheet tool YouTube instructions for spreadsheet tool github

Abstract

Stocks of fixed capital play a vital role in fulfilling basic human needs and facilitating industrial production. Their build-up requires great quantities of energy and materials, and generates greenhouse gas emissions and other pollution. Capital stocks influence economic production and environmental pollution through their construction and over subsequent decades through their use. We perform an environmental footprint analysis of total consumption, capital investment, and capital consumption in the United States for 2007 and 2012. In 2012, capital consumption accounted for 13%, 19%, and 40% of total carbon, energy, and material footprints, respectively. Housing, federal defense, state and local government education and other services (including household consumption of roads), personal transport fuels, and hospitals are the consumption sectors with largest capital footprints. These sectors provide fundamental needs of shelter, transport, education, and health, underlying the importance of capital services. Endogenizing capital causes the biggest proportional increase to footprints of sectors with low environmental multipliers. This work builds upon existing input-output models of production and consumption in the United States, and provides a capital-inclusive database of carbon, energy, and material footprints and multipliers for 2007 and 2012.

Environmental impacts of high penetration renewable energy scenarios for Europe (2016) Environmental Research Letters with Anders Arvesen, Yvonne Scholz, Hans Christian Gils, Edgar G Hertwich

Paper Feature as Resarch Highlight in Nature Climate Change

Abstract

The prospect of irreversible environmental alterations and an increasingly volatile climate pressurises societies to reduce greenhouse gas emissions, thereby mitigating climate change impacts. As global electricity demand continues to grow, particularly if considering a future with increased electrification of heat and transport sectors, the imperative to decarbonise our electricity supply becomes more urgent. This letter implements outputs of a detailed power system optimisation model into a prospective life cycle analysis framework in order to present a life cycle analysis of 44 electricity scenarios for Europe in 2050, including analyses of systems based largely on low-carbon fossil energy options (natural gas, and coal with carbon capture and storage (CCS)) as well as systems with high shares of variable renewable energy (VRE) (wind and solar). VRE curtailments and impacts caused by extra energy storage and transmission capabilities necessary in systems based on VRE are taken into account. The results show that systems based largely on VRE perform much better regarding climate change and other impact categories than the investigated systems based on fossil fuels. The climate change impacts from Europe for the year 2050 in a scenario using primarily natural gas are 1400 Tg CO2-eq while in a scenario using mostly coal with CCS the impacts are 480 Tg CO2-eq. Systems based on renewables with an even mix of wind and solar capacity generate impacts of 120–140 Tg CO2-eq. Impacts arising as a result of wind and solar variability do not significantly compromise the climate benefits of utilising these energy resources. VRE systems require more infrastructure leading to much larger mineral resource depletion impacts than fossil fuel systems, and greater land occupation impacts than systems based on natural gas. Emissions and resource requirements from wind power are smaller than from solar power.