Reliance on technical solutions to environmental problems: caution is needed.

Abstract

The world is full of examples of unintended consequences. Many solutions to burgeoning problems, whether social or technological, are later found to have unintended side effects. Sometimes these are beneficial; more commonly, they are not, and can be serious enough to call into question the efficacy of the original solution. One key area for concern is with technological solutions to our many environmental challenges. Car travel exemplifies the mixed success of technological solutions to the environmental problems it generates. At least in the cities of the Organization for Economic Cooperation and Development (OECD) countries, urban air pollution from vehicles has been greatly reduced over the past half-century. Technical emission reduction innovations include unleaded petrol, progressively lower sulfur content fuels, and three-way catalytic converters. But other proposed innovations for solving both global oil depletion and climate change may fall short of their stated aims. Improving the fuel efficiency of all vehicles promises to cut both transport oil use and accompanying greenhouse gas emissions. However, although vehicle engine efficiency has made large gains, the on-road vehicle efficiency gains (in terms of vehicle-km per MJ) have been much more modest. Reasons include preferences for larger or higher-performance vehicles, and significant power requirements for auxiliaries such as air-conditioning, information and entertainment systems, and power steering. National transport oil use and CO2 emissions are also subject to the well-known rebound effect: vehicle efficiency improvements make travel cheaper per kilometer, encouraging more travel. Furthermore, most of the world’s population aspire to the car ownership levels of the OECD countries, so total transport oil use and CO2 emissions are still growing. This rebound effect is not the fault of the technology, but of our use of it. There is yet another reason for caution: technical advances are sometimes reversed as more information about unwanted effects accumulate. Such has been the case for leaded petrol. More recently, France is considering reversing its previous promotion of diesel-fueled cars. Although diesel cars are more efficient than petrol cars, concern is mounting over the health effects of diesel’s fine particulate releases. As another example, novel chemical compounds such as chlorofluorocarbons, once though as environmentally benign (having low reactivity, toxicity and boiling point), were later found to cause ozone layer depletion. We need to be especially cautious when dealing with global problems such as climate change. One important approach for climate change mitigation is reducing fossil fuel use through much greater use of renewable energy, particularly biomass. But a recent study