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  • Material intensity in water use

    (Part of the No Sweat Solutions series.)

    Before discussing water savings, we need to define what we mean by "use." The EPA refers to withdrawal and consumption. Withdrawal is the amount taken from surface water and the water table. Consumption refers to the amount chemically combined with something (so that it is no longer fresh water) or evaporated. Water discarded instead of consumed is referred to as "returns," because it is supposedly reusable. This does not even approximate the impact of water use.

    One example the EPA gives is power plant cooling. The water is withdrawn and used to cool the plant. A little evaporates, and the rest returned (still more or less clean) to the source. This overlooks a certain amount of impact (fish killed during withdrawals, aquatic plant, fungal, and microbial growth encouraged by the change in water temperature), but is basically correct. However, they apply the same logic to water used for irrigation. With very few exceptions, irrigation water "returns" are loaded with fertilizer salts, growth hormones, microbes, and often pesticides and herbicides as well. Even runoff from organic farms usually contains salts from the manure and composts used.

    So the proper way to count water is consumption plus polluted returns -- in most cases, all withdrawals.

  • Feeding the world sustainably

    food o'plenty?

    (Part of the No Sweat Solutions series.)

    If heaven was a pie it would be cherry
    Cool and sweet and heavy on your tongue
    And just one bite would satisfy your hunger
    And there'd always be enough for everyone

    -- Gretchen Peters, "If Heaven"

    Agriculture for food and fiber represents another significant category of environmental impact. Before we worry about how to farm, we should consider how much agriculture we need. If you read the technical news, when this subject comes up it always centers on how to increase food production for a hungry world.

    This is completely misleading. There is enough food produced (including meat and fish) worldwide not just to feed everyone on the planet, not just to make everyone fat, but to make everybody morbidly obese. Counting grain, beans, roots, fruits, vegetables, nuts, and other plants and fungi (not including animal feed), plus livestock, dairy, fish, eggs, and other animal products raised for human consumption, we produced nearly 2,800 calories per person per year in 2001[1] -- including 75 grams of protein. 2,200 calories per day is generally accepted as the average needed to keep a person healthy -- neither losing nor gaining weight[2]. 56 grams of protein is the U.S. RDA for adult men[3].

    Many people have higher requirements than this -- most grown men, pregnant and lactating women, athletic women. (As one instance, Lucy Lawless used to perform gymnastics and horseback riding in fairly heavy armor ten or more hours per day while starring in "Xena - Warrior Princess," and probably burned 6,000+ calories daily at the peak of her schedule.) Children, and median-height adult women, generally need less. Below 2,200 calories, and 56 grams on average, is considered an absolute shortage; if we allow a comfort and safety margin, that would mean we want at least 2,300 calories on average per person available worldwide.

    How big an increase do we need to keep up with population growth? According to the U.S. Census[4], if you assume the same production with projected increases in population we will still average ~2,500 calories per person per day in 2010, ~2,300 per day in 2020. Without no cultivation of more acreage or increase in production per acre, we then approach absolute scarcity, falling to 1,900 in 2050. We need no increase in total food production before 2020, and only a 21 percent increase by 2050.

    Moreover, in one sense the problem of getting that increase is already solved.

  • A quick partial overview of green building techniques

    (Part of the No Sweat Solutions series.)

    What follows is a table with a (very) incomplete list of means of reducing material intensity in building. These means alone could reduce the impact of constructing buildings by about 75 percent or more, and thus greenhouse-gas emissions from construction and destruction of buildings by about half.

    Since we have green builders on this site, I invite additions to the list, especially if you can cite sources for impact reduction. I also invite comments on whether any of these are not as green as they appear at first blush.

    Note that operations account for a great deal more of the impact of building than construction. So these are green only to the extent they do not compromise operating efficiency.

    Table below the fold.