Green Options

There has been a lot of discussion over the last few years about biofuels and whether or not they are actually green, especially when produced on a large, global level.

A new study led by Marine Biological Laboratory (MBL) senior scientist Jerry Melillo says no, they aren’t green (when it comes to climate change). However, there are still many important factors to keep in mind before claiming this is the end of a long and complicated discussion.

Cow poop is a leading contributor of nitrous oxide and ammonia into the atmosphere, adding heartily to global warming. Cars, as we all know, provide their own fair share of noxious fumes to the environment. But a British team of engineers and racers is working on a way to kill two birds with one stone (metaphorically of course) by developing a race car that can run on cow poop.

Realizing that most technology found in our daily drivers was often first developed for the race track, Oaktec has announced plans to develop a manure-powered rally car, giving all new meaning to the phrase “This car runs like crap!” [ed. note: cow farts and burps contribute far more GHGs than poop, but hey, you gotta start somewhere]

Nitrous oxide, more commonly known at your dentist’s office as laughing gas, is now the most prevalent man-made substance damaging the ozone layer. And it’s a greenhouse gas. Sadly, the joke’s apparently on us.

If you picture a grain farmer out tending a field, you might imagine someone sitting on the metal seat of a tractor like the one in the picture above, moving slowly across a field - perhaps the farmer has a straw hat.  That image seems attractive as long as you are not the farmer.  Fortunately, this isn’t the real situation in the developed world or we wouldn’t get anyone in our rapidly aging population to do full-time farming on the multiple thousand-acre farms that are typical of a modern, Midwestern family farm.

Today, a progressive farmer will typically be working in an enclosed, air-conditioned cab with surround sound, a cell phone, and an internet connection for tracking commodity futures or catching up on email.  Increasingly, the tractor is driving itself by computer and GPS except for occasional intervention.  I’ve carried on a number of protracted interviews with farmers who were in just this setting.  I know one farmer that ran much of his state senate campaign from a tractor or combine.  These new, sophisticated, farm vehicles are not just about keeping the farmer comfortable and multi-tasking.  They are important tools for making farming more sustainable.

Every once in a while I come across something in the scientific literature that really surprises me.  Because there isn’t much oxygen in a worm gut, it creates the ideal conditions for these particular microbes (”de-nitrifiers”) to turn nitrate (NO3) into nitrogen gas and also generate some nitrous oxide in the process.

Nitrous Oxide

Ok, some background. Nitrous oxide (N2O) is a very potent greenhouse gas with 310 times the global warming potential of carbon dioxide. Its really an Achilles heel for agricultural sustainability because around 80% of the human-generated emissions of this gas come from farms. If even a small amount of the farmer’s nitrogen fertilizer gets converted to N2O it becomes a major part of the total carbon footprint of that field

When thinking about “carbon footprints” it helps to have real numbers to put things in perspective. The EPA estimates that for the US, agriculture represents about 8% of total human-related greenhouse gas emissions. The following is a list with a little of the detail of what makes up the footprint of an acre of a rain-fed Midwestern corn crop with a few other things thrown in for comparison. Since we grow 80-90 million acres of corn its something that matters. The values are all expressed as pounds of CO2 equivalents. If you want Carbon equivalents multiply by 12/44

My earlier blog about greenhouse gas emissions from composting generated a lot of good discussion so I am writing to respond.

• Yes, composting is certainly better than some outcomes like food scraps going into a garbage dump which does not do anything to capture the methane

• Yes, an anaerobic digester would be a very good thing to use for most waste streams.  A recent example

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Composting is a really green thing to do, right? I’ve always thought so since my Grandfather taught me to do it in the early sixties. Large-scale composting is getting to be quite the rage. The City of San Francisco attracted a great deal of attention with it’s mandatory food scrap recycling program and lots of local wineries are bragging about their use of that compost to fertilize their vineyards.

I just read today about how the Langley Parish Council in England is setting up a village compost and “set an example to small villages as the UK strives to battle climate change.”  Unfortunately, I recently learned that they and San Francisco and the Napa wineries might actually be doing is contributing to climate change.

Climate change science often ends up challenging things we think we know.

Inconvenience

The idea of composting is to provide plenty of moisture and oxygen so that microbes will digest the easily available organic matter and generate a great deal of metabolic heat in the process.  What is left at the end is a sterilized source of more resistant organic matter that can enrich a soil. 

Composting

of wastes is done with very good intentions, but there is the inconvenient truth that even a very well run large-scale compost operation emits some methane.

But if you stop to think about it, as much as you intend to have oxygen available to the whole pile (aerobic conditions), there are definitely going to be micro-sites that are going to lack oxygen (anaerobic conditions) particularly when there is huge oxygen demand during the peak of the process. That is where methane gets made.

With Congress deep in debate over legislation aimed at the prevention of global warming, and skeptics ramping up their rhetoric, it seemed like a good time to take a step back to some basics — more accurate information is critical here. Step one in figuring in out how we can help in the battle against climate change involves answering questions like “What are the major causes of global warming?”

What causes global warming?

Scientists have understood the greenhouse effect since the early 19th century; the first paper on the topic was published in 1896. Essentially, certain gases trap energy from the sun: according to the Intergovernmental Panel on Climate Change’s Fourth Assessment Report, greenhouse gases “act as a partial blanket for the longwave radiation coming from the surface. This blanketing is known as the natural greenhouse effect.”

What are greenhouse gases?

Several compounds contribute to the greenhouse effect, including