Your mom was right: eat your green vegetables! The United States Department of Agriculture (USDA) has released an update to the classic food pyramid - that great visual aid that reminds us we eat too much garbage. The new pyramid, though, is much more individually tailored, interactive, and interestingly is more like a pie than a pyramid.

The classic food pyramid is built from the bottom up: the lowest layer being the foods you should eat the most, the top layer the stuff that's tasty but not so good for you. The new pyramid is like a slice of pie that has been cut into several smaller slices. Each slice represents one of the following food groups: grains, vegetables, fruits, oils, milk and protein. The thickness of each slice represents the relative amounts of each type of food we should be eating.

On the surface, the changes to the new pyramid are mainly cosmetic, but delving a little deeper, we see that there are specific recommendations regarding each slice of the diet pie. At least half of our grains consumption should be whole grains, such as brown rice, whole wheat breads and pastas, and (hooray!) popcorn. We should be eating more dark green and orange vegetables, as well as lots of fruit. The guidelines, however, encourage more actual fruit and less fruit juice, though 100% vegetable juice is still okay.

Another major change to the pyramid is the description of "discretionary calories" and a recognition that not everyone eats the same way. Discretionary calories are the other stuff of food - desserts, snacks, pop and booze. The pyramid recognizes that most of us are going to consume things that aren't entirely good for us, and that we can plan for these moments of weakness and maintain good eating habits while occasionally indulging ourselves. This pyramid also easily includes vegetarian diets, offering many alternatives to meat, though it continues to recommend dairy products.

Exercise is the pyramid's third dimension, visualized as a figure running up steps on the side of the pyramid. This emphasis shows a strong focus on overall health rather than just diet, and physical activity is strongly promoted throughout the accompanying discussion. This exercise focus seems like a new attempt to address the sedentary lifestyle of much of the US population.

All this information is found at the USDA's food pyramid website, which offers an interactive way to tailor the guidelines directly to you. There are details on all the types of foods and a handy way of measuring units of food. The charts showing common servings converted to cups or ounces alone are worth a trip to the site. For example, I now know that 2 medium carrots is about a cup. I expect my recipes to turn out a little better now.

Bacteria make cheese and make you sick, but now they can also make energy and clean wastewater in the process. A new device, invented at Penn State University, has created some sensational possibilities in the growing field of renewable energy. The device is a Microbial Fuel Cell (MFC) and possesses the ability to yield a substantial amount of hydrogen gas as the product of breaking down dissolved organic waste.

The chemical process underlying the mechanism is called hydrogen fermentation - a reaction similar to the process that creates alcohol - in which bacteria break down carbohydrates into hydrogen atoms. Although this reaction has previously shown promise for hydrogen production, it has had a "fermentation barrier" limiting both the hydrogen output and the break down of the organic matter. The new MFC stimulates the bacteria with a small amount of energy - 0.25 volts - and removes this barrier, increasing the hydrogen production 4 fold and allowing the complete processing of the organic waste. Most wastewater treatment plants function by letting waste sit in giant vats until bacteria break down the guck into simpler molecules suitable for return to the environment. If MFCs could be coupled to this process, valuable hydrogen gas could be captured as human or agricultural wastewater was being cleaned.

Hydrogen is a promising alternative to fossil fuels since it is a clean fuel; the product of its combustion is simply water. The actual impact of this science, however, has thus far been limited to concept car designs and eco-friendly Shell ads on the back cover of Harper's - there is yet to be a hydrogen creation method that is cost effective. The new fuel cell is probably not significant enough to jump start a booming hydrogen economy, but Dr. Bruce Logan, the creator of the device, is realistic about the fuel cell's uses. "This form of renewable energy production may help offset the substantial costs of wastewater treatment as well as provide a contribution to nations able to harness hydrogen as an energy source." Let's just hope that when they make the hydrogen gas stations, they don't all smell like sewage treatment plants.

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