Listed below are recent posts across all of CalRecyle's blogs.

  • The Greening of Commercial Compost

    Compost happens, as they say in the biz.  It’s true that, given enough time, most natural materials will decompose.  The whole idea behind “composting” is to optimize nature’s process by providing the right mix of carbon, nitrogen, water and air. Most commercial-scale composting in California is done in long, narrow piles called windrows, which are mixed regularly by a specialized piece of equipment called a windrow turner.  These enormous, diesel-powered critters range from 200 to 600 horsepower, but you’ll be traveling in hours per mile not miles per hour.  What if there was a way to replace some of that diesel using the sun?


    CalRecycle was involved in in a project, funded by the San Joaquin Valley Air Pollution Control District, involving the Association of Compost Producers, private consultants and local partners,  to see whether large piles of green materials could be composted  using small “bounce house” blowers powered entirely by the sun to pump air into the pile instead of being mechanically turned.  The point of the project was so see whether air emissions could be reduced during the first three weeks of composting, which is the time when most emissions of volatile organic compounds—aka VOCs—occur.  VOCs are important to the air district because they mix with oxides of nitrogen (NOx) from vehicle tailpipes to form ozone, a very dangerous air pollutant at ground level. Summer ozone levels in the Central Valley are some of the highest in the country, and per the federal Clean Air Act must be reduced.

    The same sunlight that helps VOCs and NOx turn into ozone can provide more than enough electricity to power a 1.5-horsepower electric blower using only one solar panel, and that energy can be stored in batteries so that pile aeration occurs day and night. A series of pipes laid under the composting material provide a path to inject air into the bottom of the pile, and it filters up to the top, keeping things happily aerobic.  To trap more emissions, the tops of the piles are covered with a layer of finished, unscreened compost, and kept damp with sprinklers, again sparing the air because the diesel-powered water trucks so common at windrow facilities get a little rest. 


    VOC emissions were reduced in this pilot project by 98 percent, diesel use was reduced by about 87 percent during those critical first few weeks of composting, GHG emissions were reduced by about half, and the amount of water used to keep the pile moist was reduced by 20 percent.  That’s quite a savings.  

    To reach California’s goal of 75 percent recycling and composting by 2020, and ARBs draft goal to get 90 percent of organics out of landfills by 2025, many new compost facilities will be needed.  No one type of facility will fit all communities, but all new organic materials handling sites will need to have 21st century infrastructure that protects air and water quality, and they will have to be good neighbors.  The aeration system for the pilot project cost less than $15,000 per zone, which is pretty affordable considering a new diesel windrow turner would likely set you back half a mil.  

    Solar panel prices keep coming down, and efficiency is still going up, so it looks like solar-powered aerated static piles are a good option for community-sized compost sites, and probably could be scaled up quite large.  Already, several compost operators are looking at adopting this technology.  

    The full report on the project can be found linked to the very bottom of this page:

    –Robert Horowitz
    Robert Horowitz is a Supervising Environmental Scientist at CalRecycle.

    Posted on In the Loop by Robert Horowitz on May 23, 2016

  • Home composting – what are you waiting for?

    You conserve water, you recycle, and you use environmentally safe products around the home. What else can you do to reduce your carbon footprint?

    It’s time to start composting!

    Don’t be afraid. The scary stories about rats and odors have been blown out of proportion. You don’t have to perfectly balance the “greens” and “browns” to avoid a full-blown catastrophe, and you don’t need to keep the pile at a specific temperature. In my years of composting in a semi-urban setting, I have yet to see a rat, or even a little mouse, anywhere near my bin. And, my pile has never gotten even a little bit foul-smelling. The main creatures I see are worms, and the only smell I’ve encountered is a nice, earthy, rich-soil smell. I sometimes err on the side of too dry/too many “browns” to keep the risk of rodents and smells down, which results in a slower decomposition process. But eventually, I get great compost. And, in the meantime, I’m keeping a lot of organic waste out of landfills, where it would break down in a seriously catastrophic way (i.e., anaerobically, without enough “browns”) and release greenhouse gases. I don’t even garden that much these days; I just like the thought of turning my leftover food into good stuff rather than bad stuff.

    The main point here is that composting is not tricky or scary, and you don’t have to be overly specific about the balance, especially if you’re not in a big hurry to create fabulous soil amendments. A variety of material is nice, but not necessary. (Let’s just say my pile is heavy on soggy coffee grounds and filters, plus brown leaves from the one big tree in my backyard.)

    Here are some websites with very basic instructions for starting a compost bin – I chose them for their low intimidation factor:

    U.S. EPA: Composting at Home

    Rodale’s Organic Life: The Easiest Way to Compost

    Planet Natural: Composting 101

    You can go out and buy stuff, like a bin, an aerator, and some fancy container for your kitchen scraps. Or not! Some people build their own compost systems. The options are seemingly endless (as is the price range). As for kitchen scraps, you can use any container with a lid and keep it in the refrigerator, clearly marked “compost,” until it’s full.

    Once you’ve read through the webpages above and are familiar with the basic concept of “green” and “brown,” if you still want to simplify, you can follow my own compost recipe:

    • Start with Brown. Add Green. Add Brown. Water with a hose with a spray nozzle, until the pile is about as damp as a wrung-out sponge. Cover and forget.
    • The next time you add to your pile, alternate Green and Brown, ending with Brown, and water with a hose with a spray nozzle. Poke the whole thing a few times with a shovel or pitchfork. Cover and forget.
    • Do the same thing the next time … and the next time.
    • Now and then, when you’re in the mood, take your shovel or pitchfork and really mix up the whole pile, or even “turn” it so the stuff that was on the bottom is now on top, and vice versa. There might be some good compost at the bottom, which you can separate out, let sit for a few weeks, screen out the big chunks if you want, and apply it to your garden.

    It’s hard, as an environmentalist, not to get a little wistful when you check on your bin and see that your slimy, fuzzy, leftover produce does not exist anymore but has been replaced with great-smelling, rich, dark compost. Once you see that, you might wonder why you waited so long to start.


    Posted on In the Loop by Heather Jones on Apr 28, 2016