An engineer tackles his personal carbon use

“On May 2, after nightfall shut down photosynthesis for the day in Hawaii, carbon dioxide levels in the atmosphere touched 400 parts-per-million there for the first time in at least 800,000 years.”

Scientific American


Scientists believe that if everybody on the planet emitted two and a half tons of carbon dioxide or less each year, the human race could carry on forever without worrying about climate change. Unsurprisingly, however, current rates far exceed this target. The average global level hovers around five tons per head, and in wealthy countries the figure is far higher. In the United States, each individual produces around 20 tons of carbon dioxide annually.

Like many of my generation, I became acutely aware of the need for energy conservation during the 1970s oil crisis. At that time, the conversation was purely about reducing oil consumption; carbon emissions and climate change hadn’t yet become household concerns. But this firsthand experience of the volatility of our energy system got me started thinking about ways to minimize my personal impact.

I tried to reduce my energy usage in small ways — turning off the lights when leaving a room, setting the thermostat a few notches away from the ideal temperature — while tackling the problem at the other end of the scale as an engineer on large-scale projects. As the years passed, however, I felt the need to deal with my own carbon footprint in a more systematic fashion. Around 2000, I set out on a quest to reduce my environmental impact. Together with the family members with whom I share my New Jersey home — my wife, mother, and three children — I’ve spent over a decade tracking and mitigating our carbon dioxide emissions.

In the United States, each individual produces around 20 tons of carbon dioxide annually

As an engineer, I have tried to be as rigorous as possible in this effort. And as funny as it may sound, the most effective tool I’ve found is a website called The site’s well-researched and fairly comprehensive calculator walks users through the various facets of their lives and prompts them to put in the appropriate details, then does the calculations.

Planes, trains, and vegetables

One of the first issues we dealt with was transportation. Living in the New York metropolitan region (in suburban New Jersey), we take advantage of public transportation whenever feasible. But many of our trips do require a car, and among four drivers we clock up about 25,000 miles annually. We were early adopters of the Toyota Prius, buying our first model in 2001. In the past few years, 80% of our driven miles have been in a Toyota Prius, at an average of 42 miles per gallon — about half the national average rate of consumption.

Food also plays a major role in a household’s carbon footprint, and vegetarianism in particular is a highly effective strategy for curbing emissions. According to the United Nations Food and Agriculture Organization, “livestock production generates nearly a fifth of the world’s greenhouse gases — more than transportation.” By simply not eating meat, my family produces fewer emissions than the average American household.

We’ve also significantly reduced our electricity consumption. Installing a high-efficiency heating and cooling system with sophisticated controls had a surprisingly profound impact, and replacing light bulbs in the house with compact fluorescents also helped. We use natural gas for heating, as it produces fewer emissions than oil. I would ideally like to install an electrically driven ground source heat pump system, but that’s a few years in the future.

The 8.4 kilowatts of photovoltaic panels we installed on our roof in 2011 now generate about 60% of our annual electricity demand. Given the federal and state incentives we were able to take advantage of, the installation will pay back in under ten years. That’s a better rate of return than most other investments today.

Vegetarianism in particular is a highly effective strategy for curbing emissions

So close, but so far away

An average family of six in the US emits 120 tons of carbon dioxide every year; we’re down to 50. This is clearly a step in the right direction, but it’s still three times the sustainable level of emissions.

Ironically, one of the main things holding us back is my job, which largely involves advocating for sustainable design. About 18 tons of our CO2 emissions — over one third of my family’s total — come from my business-related flights.

For all the carbon dioxide that we’re still emitting, I buy offsets. We’ll keep trying to lower our consumption through technological and behavioral means, but for the moment this is the only practical way to be carbon neutral. It costs us about $1,500 a year, and we have to take it on trust that the money will indeed be spent on projects that will generate the advertised carbon reductions. That’s not entirely satisfactory.

Scaling the impact

Although I’ve been leading sustainable design projects for decades, my family’s experiments have given me new insight into the day-to-day realities of carbon emissions. Being able to speak from personal experience has proven extremely useful in my work at Arup, as well as in my class at Princeton, where I work with architecture students to design net-zero carbon buildings.

For a variety of reasons, none of them technical, we have very few examples of constructed and operational net zero carbon buildings to illustrate the genre. But there’s a growing demand, and we will continue to push the envelope of what’s possible at every opportunity.

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