Detergents 3%

Vehicle travel21%

Pets3%

Home energy 2%

Air travel5%

Human diet40%

Landscape26%

Carbon: 8,186 kg per year

Our Household Choices in Urban Living: Understanding Nutrient Cycling in Twin Cities Homes

Thank you for participating in our May 2008 survey entitled “Our Household Choices in Urban Living,” spon-sored by the University of Minnesota. Over 3,000 households in Ramsey and Anoka Counties responded to the survey, answering questions about everyday activities such as transportation, yard management, food consumption, trash and recycling, and home energy use.

From your responses, we are learning more about how household activities influence the cycles of three main nu-trients: carbon, nitrogen and phosphorus. These nutrients are essential for all living organisms, but too much in one place can also contribute to air and water pollution. A better understanding helps us keep the landscapes we prefer, reduce air and water pollution, and make plans for healthy and satisfying lives. The choices you make at home can become part of the solution.

Water pollution – Three quarters of the nitrogen that moves through our average household comes from the food we eat (nitrogen is an important part of protein), or the lawn fertilizer we use. Some of this nitro-gen eventually ends up in our water-ways. Excess nitrogen in rivers and lakes can feed algae blooms that cause lower water clarity and oxygen levels, bad odor and taste, and the loss of desirable species.

Air pollution – When fossil fuels are burned in power plants, home

furnaces, or vehicle and airplane engines, the high temperatures convert atmospheric nitrogen (N2) into various nitrogen oxides (NOx) that contribute to smog, acid rain, and other

problems. One-quarter of our average household’s nitrogen

comes from these sources.

Nitrogen: 54 kg per year

Landscape9%Human

diet4%

Air travel8%

Home energy

39%

Plastic1%

Paper2%

Vehicle travel37%

Most people think of carbon as carbon dioxide (CO2), the main contributor to global warming. Eighty-four percent of the carbon used by our average household comes from fossil fuels (such as oil, coal, or natural gas) that are burned for home energy, vehicle travel, or air travel. This carbon immediately enters the atmosphere as carbon dioxide.

But carbon is the backbone of all organic molecules, not just oil. Carbon is a major component of people, plants, animals – even plastics! The other sixteen percent of a household’s carbon comes in through food, paper, plastic, or is used by the growing plants in our landscape.

Nutrient Cycling in an Average Twin Cities Household What activities contribute to a household’s nutrient budget?

Detergentsetc.39%

Human diet52%

Pets9%

Carbon: Driving, flying, and home energy create most of a household’s carbon emissions. If you drive to work every day, you can reduce your commute carbon use by 10% if you carpool, bus, bike, or telecommute just one day every other week! (see www.metrotransit.org for ideas) The bottom of this page has more ideas and resources for reducing home energy use.

Nitrogen: If you use more lawn fertilizer than your grass needs, the excess nitrogen becomes water pollution. Look through the University of Minnesota extension recommendations (snipurl.com/n-fert) to estimate how much fertilizer your lawn needs. Leaves and grass clippings on driveways, sidewalks, or the street wash into your local lakes and streams, so mulch them into your lawn or compost them (either on your property or at the county compost facility). Driving and flying less will help with nitrogen, too, as well as carbon.

Phosphorus: Phosphorus is restricted in lawn fertilizer in Minnesota — make sure you don’t use garden fertilizer by mistake! Read the label on your bag of fertilizer and look for a set of three numbers like 23-0-6. The middle number is the percent phosphorus, so this should be a zero. If your pets use the outdoors, scoop their waste, bag it, and put it in the trash. The landfill can handle the phosphorus better than the waterways can.

Over 50% of Anoka and Ramsey County respondents have taken actions to reduce home energy use that will not only reduce carbon emissions, but also save on energy costs.

These actions have a real impact on a household’s carbon budget. While we can’t predict exactly how much carbon a particular household will save, our survey results show that even small actions create meaningful improvements. For example, using fluorescent bulbs, installing a programmable thermostat, or lowering the heat by two degrees F in winter each result in an average 4% reduction in home-energy carbon emissions.

For more ways to lower your emissions, check out www.energy.gov, www.mnenergychallenge.org, and sustainablechoices.stanford.edu. There are many things you can do to help create solutions, from simple first steps to larger commitments. Which ones are right for you?

Reducing Your Home Energy Use:

We’re All in This Together More than half of Anoka and Ramsey County respondents were “concerned” or “very concerned”

about negative environmental effects influencing their quality of life. Fortunately, there are many ways to make improvements.

Phosphorus: 4 kg per year

Sixty percent of a household’s phosphorus comes from human and pet food (phosphorus is an important part of DNA and other parts of our cells). The remaining forty percent has not been well studied, but appears to come from various detergents and other household products that wind up in a household’s wastewater. Most of the phosphorus that goes into the city sewer eventually goes from the wastewater treatment plant to the landfill. Septic systems, un-scooped pet waste, and leaves and grass clippings that wash into the gutter can be sources of phosphorus (and nitrogen) pollution to our lakes and streams. Phosphorus is often more important than nitrogen in feeding noxious algae blooms.

The first step in making any changes is to see where you are. From our survey results, we’ve identified a few key activities that are major contributors to a household’s carbon and nitrogen emissions. All units are in kilograms of carbon or nitrogen, per household, per year (one kilogram = 2.2lbs; 1000kg = one metric tonne). Next, set a goal for reducing your emissions. Ten percent is a big improvement — and it’s easier than you might think! Take a look at some of the ideas and websites on the previous page to find what works for you. Finally, track your progress by filling out this calculator again next year. Did you meet your goal?

Your Household’s Nutrient Budget Survey Average

Electricity:

______________________________ x 0.19 = _____________________kg C/yr (your annual electricity use in kwh) ← available by calling your utility Total home

energy carbon: 3261 kgC/yr Natural Gas:

______________________________ x 1.49 = _____________________kg C/yr (your annual natural gas use in therms) ← available by calling your utility

Vehicle Travel: (MPG estimates at fueleconomy.gov Add additional vehicles if needed)

Vehicle #1: _________________ ÷ _________________ x 2.24 = ___________________kg C/yr (miles per year you drive) (your vehicle’s mpg)

Vehicle #2: _________________ ÷ _________________ x 2.24 = ___________________kg C/yr (miles per year you drive) (your vehicle’s mpg)

Total vehicle travel carbon: 3013 kgC/yr

Air Travel: (Distance calculator at snipurl.com/airdist Add additional flights if needed)

Flight #1: ___________________ x _____________________ x 0.0067 = ______________kg C/yr (roundtrip distance, miles) (# of family members making the trip) Flight #2: ___________________ x _____________________ x 0.0067 = ______________kg C/yr

(roundtrip distance, miles) (# of family members making the trip)

Total air travel carbon:

624 kgC/yr

NITROGEN:

Lawn Fertilizer: Look on the fertilizer bag for how many pounds per bag, and also a set of three numbers. 23-0-6 is common for lawn fertilizer. These three numbers are the percentages of nitrogen, phosphorus, and potassium, respectively.

____________________ x _________________x 0.0045 = ________________kg N/yr (pounds of fertilizer used) (first number on bag, e.g. 23-0-6 )

— use either of these calculations, but not both —

Alternately, you can estimate your fertilizer use based on the number of times you apply fertilizer (we assume a standard application rate of 1lb nitrogen per 1,000 square feet). If you hire a lawn care company, use this equation and enter “3.25” for the number of times you apply fertilizer.

____________________________ x _________________x 19.8 = ________________kg N/yr (number of times you apply fertilizer) (area of your lawn in acres)

Total lawn fertilizer nitrogen:

13 kgN/yr

CARBON:

What about PHOSPHORUS? Most of our average household’s phosphorus comes from human and pet food. It is not possible to eat “low-phosphorus” food, since phosphorus is an important part of all the plants and animals we eat. You need this phosphorus to make DNA, teeth, bones, and many other parts of your cells. The other forty percent of the phosphorus is very difficult to measure and track directly, but you can look for phosphorus-free detergents and other household products to help reduce your phosphorus use.

Tracking Your Own Nutrients

www.tchep.umn.edu

What’s coming up next? An expanded, online version of our Household Flux Calculator Science Museum of Minnesota’s “Future Earth” exhibit and

“Science Buzz” online community dialogue University of Minnesota Bell Museum’s “Shelter” exhibit Check back on our website for updates and exhibit dates

Special thanks to the three thousand residents of Ramsey and Anoka Counties who contributed their time and energy filling out our survey. This would not have been possible without your help. Additional support from the University of Minnesota-Twin Cities (Ecology, Evolution, and Behavior; Fisheries, Wildlife, and Conservation Biology; Forest Resources; Soil, Water, and Climate; Water Resources Center), the University of California-Santa Barbara (Geography), the National Science Foundation, and Cedar Creek Ecosystem Science Reserve.

How do household activities influence the cycles of carbon, nitrogen, and phosphorus in urban and suburban ecosystems?

Department of Forest Resources University of Minnesota 115 Green Hall 1530 Cleveland Ave. N. St. Paul, MN 55108-6112