Getting Creative with Compost Ingredients

There's no special trick to successful composting other than ensuring a good mix of greens and browns. But there is an endless list of things that might be good -- or might be wrong -- to add to your compost.

The Good

Though potentially off-the-wall, these items can actually increase the overall benefits of your compost:

• Clay - Soil should be a good mix of organics, sand and, yes, even clay. The clay in dirt can even help capture nitrogen (as ammonia) before it escapes from your pile. (Don't add modeling clay.)


• Egg shells - These add calcium to the soil. (Don't compost rotten eggs.)


• Granite dust or greensand - This adds several trace elements. You can get granite dust at tombstone manufacturers. (Greensand is just a term for rock dust.)


• Hair - This sounds icky to me, but human and pet hair contains lots of nitrogen and composts nicely I hear.


• Junk mail - This is the most satisfying thing to tear up and throw in a pile! (But see glossy paper below.)


• Oyster shells - Either whole or preferably crushed, these add calcium.


• Seaweed - Seaweed contains lots of nitrogen. Wash it down first to remove salt.


• Soil - Some gardeners like to jump-start their compost by introducing extra organisms from soil. Though all organisms needed for decomposition already exist on plant material, adding a few shovels-full of soil can't hurt.


• Wallboard or drywall - Crumble it up as much as possible, and don't over-do it! Drywall is made of gypsum, which includes lots of calcium.


• Wood ashes - Wood ashes from non-pressure treated wood are high in potassium and can be used sparingly in compost. Don't use more than one or two shovels-full per batch since ashes are very alkaline and will disrupt the pH of your finished compost. (But see below for coal or BBQ ashes.)

The Bad

These things can go into compost if you're really, really good at composting, but the average gardener should avoid them:

• Dairy products - Same issues as meat (below).


• Diseased plants - Your pile would have to get awfully hot to kill all viral pathogens. Bag diseased plants at your plot and take them home for disposal.


• Fat or lard - Same issues as meat (below).


• Human urine - Though urine from a healthy person is sterile and contains lots of nitrogen, don't include it at our community garden. You can give it a try in your home compost if you must.


• Meat scraps - It takes a very specific set of conditions to safely decompose meat or dairy products. It's very hard for the average gardener to reproduce these conditions.

The Ugly

Strictly verboten! Never ever, ever put these things in your compost. At best they won't decompose, at worst they may cause disease in humans!

• Animal urine, feces, or litter - Cat feces in particular can contain parasites that cause brain damage in toddlers, infants, or unborn children. (Pre-composted horse, cow, rabbit, chicken manure or manure from other vegetarian animals is fine to add to your compost.)


• Coal ashes - These ashes contain harmful chemicals, even after burning. Don't use BBQ grille charcoal ashes either.


• Glossy paper - Don't compost glossy paper, catalogs or magazines. They include special clays and inks that aren't the best for your soil. Don't compost paper with colored ink either.


• Human feces (including diapers) - Leave it to the city to try to figure out how to deal with your poop! It can contain all kinds of viruses, bacteria and other diseases like dysentery, e. coli, and cholera. Even composted human waste from municipalities should never be used on food crops.


• Metal, Plastic or glass - These items will simply never decompose. Broken glass in the soil is obviously dangerous to gardeners.


• Pesticides, herbicides or fungicides - These will kill the very organisms you're trying to encourage in your compost!


• Petroleum products - Liquid petroleum products will poison the soil and groundwater. One measly pint of gasoline can contaminate 750,000 gallons of water.


• Pressure treated wood or sawdust - Pressure treated wood contains cyanide and/or other chemicals that kill beneficial soil organisms.

More Reading

Lists of other things you can or should not put in your compost:

Compost Ingredients at MasterComposter

All About Materials by Steve Solomon

What can I compost? at the HDRA

Materials for Better Composting at the Chicago DOE


Copyright © 2003 Brian Ballard. All rights reserved.

When Your Garden Sleeps, It Dreams

This winter it may seem nothing is happening in your garden. Biological activity slows down in the colder months, organisms go dormant or migrate deeper into the soil, cool season weeds like chickweed get their first footholds, and rains wash nutrients and important minerals away. You don’t have to be a helpless observer of this hibernation. Use the winter months to rebuild your soil.

Once your garden is done for the season, clear out the last of your annual plants saving them for compost. Reserve a small part of the garden for your fall and winter greens and for planting garlic cloves in November. Cover the rest of your soil with a nice layer of compost materials about 8-12 inches deep. Be sure to use both “greens” (grass clippings, coffee grounds, fresh chopped plants, composted manure) and “browns” (fall leaves, non-pressure treated sawdust, dry plant material) in the mix.

A variety of amendments help replenish the supply of important minerals. Agricultural lime is a good source of calcium, and dolomite lime also includes magnesium. Calcium helps plants build cell walls. Magnesium is the working ingredient in chlorophyll. Both types of lime help neutralize acidic soil, which is also a side effect of too much rain.

A compound called greensand includes a different mixture of beneficial minerals including potassium, iron, and phosphorus. It’s usually available at better garden centers.

You can even use granite dust to add a wide array of minerals to your soil. If you look closely at granite, you’ll notice it’s made up of thousands of different crystals fused together. Each crystal is essentially a different mineral, including many that plants require in tiny amounts: potassium, calcium, iron, magnesium, phosphorus, manganese, and others. These minerals become more available when ground into gravel, or even into dust, and are broken down further by organisms and naturally occurring weak acids in the soil. Ready sources of granite dust include stone yards, or gravestone monument carvers.

Spread a few handfuls of lime, greensand, or granite dust over your compost mix and work it in a bit. Water the mulch well, and cover it with two layers of burlap. The burlap works as insulation, keeping the soil and sheet mulch slightly warmer than the air, and provides the dark, moist environment soil organisms prefer. Most coffee roasters will gladly give you discarded burlap bags their raw coffee beans are shipped in.

Once or twice during the winter, pull back the burlap and turn your compost mix, covering it again with the burlap when you’re done. In the spring, you should be able to remove the burlap and either plant directly into the finished compost, or work it into your soil a bit if it’s not completely done.

Copyright © 2006 Brian Ballard. All rights reserved.