I bought compost from the city of Port Angeles and in a sifted wheelbarrow of compost I got three gallons of pencil diameter “twigs”. These are not composted. They break/snap and are green inside. The compost was supposed to be tilled into the garden and flower beds but somewhere in the back of my mind I sort of remember that this will take nitrogen out of the soil to compost down. Is that correct or should I not be concerned?
It sounds like screening your compost was a good place to start; Mike McGrath recommends removing the “odd original ingredient” from compost this way in his Book of Compost (New York, NY : Sterling Pub. Co., 2006). Woody material should definitely be removed, he says. If your compost does not seem otherwise ‘off’ (an ammonia smell, a sulfurous smell, very odd color), sieving off the woody material is often sufficient.
Twigs compost more slowly than other material, and you could, if you like, simply re-compost them, according to the King County Solid Waste Division.
There is some debate over the effects of inadequately decomposed material such as your woody twigs in compost and mulch. Linda Chalker-Scott addresses the question of less-than-fully composted yard waste in her May 2003 myth. She agrees that inadequately decomposed yard waste has a reputation of removing nitrogen from the soil, but writes that the way the yard waste is used affects the way it interacts with the soil. As a mulch (a layer over the soil to prevent weeds or retain moisture), it does not significantly reduce soil nitrogen, but as a compost (incorporated into the soil), it may reduce nitrogen in the soil.
If you are still concerned about the quality of your compost, Stu Campbell suggests using the following techniques on municipal compost in his Mulch It! (Pownal, Vt. : Storey Books, 2001) First, test the pH, and, if it is off, store and turn the compost for several months before using it. Mature compost should have a pH between 6 and 8,
which you can test using a soil test kit or some of the other options listed on Cornell University’s composting pages.