Help your soil and comply with California's new green waste law by composting

·4 min read

A new law went into effect Jan. 1 that requires Californians to separate organic material from their other wastes. It’s a landmark reform that will transform the state’s throwaway culture, ease pressure on landfills and also reduce the climate-warming fallout of our usual trash system.

Senate Bill 1383 was passed and signed into law in 2016 by Gov. Jerry Brown. It mandates that Californians put unused food, coffee grounds, eggshells, banana peels and other leftovers into the bins that they use for other “green” waste, such as garden trimmings, lawn clippings and leaves.

Don’t toss those leftovers: Mandatory food recycling to begin in California Jan. 1

When organic materials go into landfills they decompose and produce a fifth of the state’s methane, a greenhouse gas that is more potent than CO2 in warming the planet and causing our climate crisis. Organic materials make up about 50% of landfill materials. Instead of being a problem, these materials will be recycled into compost or mulch that can improve our soil and this is certainly good for our gardens.

There will be penalties for lack of compliance. Individuals and businesses that don’t separate wastes can face fines up to $500 per day and cities and counties out of compliance could pay as much as $10,000 a day per violation.

Grocery stores must donate food that would otherwise be thrown away to food banks or similar organizations. This is a win-win for sure. I also found out that there is a two-year grace period before fines start which perhaps explains why there are no green waste bins at my home yet.

A compost thermometer aids in monitoring temperature.
A compost thermometer aids in monitoring temperature.

I won’t need to worry about this new law because I already compost kitchen wastes, spent flowers and garden plants, leaves and lawn clippings. I think that sending away such nutrient-rich materials to a landfill is a bit on the crazy side. Throwing away the by-products of my living and my landscape tends to impoverish my soil over time — so I don’t want to be foolish and not keep soil nutrients where they should stay.

Composting is not rocket science although there are some basics that you need to know to get good results. So I am going to relay to you the basics here but for more information on composting see bit.ly/33T7wYw.

First of all, a compost pile or bin should be at least 3 feet by 3 feet by 3 feet. This will assure enough material to heat up and you will want the material to heat up to about 140 degrees or more which will destroy most weed seeds and pathogens. A compost thermometer will be a boon to monitoring temperature.

The heat is caused by the many microorganisms — fungi, bacteria — that are at work breaking down the organic material in the pile. All they need to do their work is moisture, oxygen. This is why it is important to turn the pile or stir it to keep oxygen available and to add moisture as the pile is constructed. The pile needs to be moist, but not sopping wet. The more frequently the pile is turned the faster that composting will be completed.

This breakdown of this material will work best if the ratio of carbon to nitrogen (C: N) in the pile is about 30:1. How does one arrive at such a ratio?

To achieve some approximation of this it is good to know the carbon to nitrogen ratios (C:N ratio) of materials going into the pile. Leaves have a C:N ratio of 60:1 whereas fresh lawn clippings have C:N ratio of about 20:1. Coffee grounds are about 20:1.

In the composting world higher carbon materials are called browns and materials higher in nitrogen are referred to as greens.

Browns are sawdust, straw/hay, fall leaves, pine needles twigs, chipped tree branches/bark, corn stalks, wood chips, paper (newspaper, writing/printing paper, paper plates, napkins, and coffee filters), dryer lint, cotton fabric, corrugated cardboard (without waxy/slick coatings).

These modular compost bins make it easy for the home gardener to turn or store compost.
These modular compost bins make it easy for the home gardener to turn or store compost.

Greens are lawn clippings, plants clippings, green weeds, manure from horses, sheep, chicken or rabbits but not from dogs or cats, coffee grounds/tea, kitchen wastes (vegetable and fruit scraps), seaweed.

It is not an exact science to get to the proper C:N ratio so one needs to try to get as close as possible by mixing the two types. One formula that seems to work would be half manure and coffee grounds mixed with half straw, hay or fall leaves. The pile can best be built by alternating layers of greens with layers of browns.

I have found that re-stackable modular compost bins work well for making compost. Information on constructing these can be found at bit.ly/3KLsnxu.

Happy New Year and happy composting.

If you have a gardening-related question you can contact the UC Master Gardeners at (209) 953-6112. More information can be found on our website: sjmastergardeners.ucanr.edu/CONTACT_US.

This article originally appeared on The Record: Gardening: Help your soil, comply with new green waste law by composting

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