This week we are tackling a few more questions in our Compost Q & A series, with Master Composter, Sarah Ferry. Here are some more great questions from Simple Organic readers, taking a look at topics like bacteria in compost piles, paper products, and looking at the issue of composting pet waste, which we touched on once before.

Simple Organic: I always thought that you could compost anything from your garden. But then a farmer in our area told us never to compost tomato plants. He said that our humongous pile of composting material we now can’t use on our garden because of the bacteria that tomato plants can grow. Is that true?

Sarah Ferry: This is an area of debate, but essentially you can add many things to a compost pile if the pile is properly managed and gets hot enough (to at least 150 degrees). When the pile becomes hot throughout, the heat kills the pathogens that are present.

However, most backyard composting systems do not regularly reach this level of heat to kill every pathogen in the diseased plant so if a plant in question carries disease (such as tomato plants), it is always best to leave it out. If you can be certain that you can maintain a temperature of 150 degrees throughout the pile the heat should kill most pathogens but it is best to err on the side of caution if you are not sure your pile is reaching this temperature regularly (it is a great idea to invest in a compost thermometer to see how hot your pile is getting!).

SO: I’m curious about paper products. We garden organically and I’m always a little reluctant to put shredded paper in the compost because so many papers and inks are treated with nasty stuff. Any suggestions on what’s safe for organic veggie garden mulch and what’s not?

SF: This is really a personal call. If you are serious about being purely organic then you may want to forgo the dyed paper and ink to “certify” your land as purely organic.

In my opinion, however, the little bit of inks and dyes are not harmful enough to effect the quality of produce especially once the pile becomes hot enough to really break things down. If you are using the paper in a worm bin this is especially the case.

Photo by kirybabe

My personal belief on this issue is that in composting the paper, you are being far more environmentally sustainable than shipping it away to be recycled which uses far more fossil fuels and energy than we would want. I like to close the loop as close to home as possible. Stick to the regular or newspaper type paper, and leave out the glossy stuff.

If you are really worried about the organic integrity of your garden, but would like to reduce the impact on the environment- you may want to consider adding a worm bin to let the worms digest this paper (they love it!) and use the worm tea on your ornamentals.

SO: In my research I learned that you CAN compost dog waste with the worms, but you should not add food items, only the “bedding” and dry matter. Any thoughts on this?

SF: Ok, you got me– If you are really serious about it, you can compost dog waste- but you would not want to mix this in to your normal compost bin that you are using for other items. You also would not want to put this finished compost on your garden (perhaps just your lawn or ornamentals), unless you are getting them sufficiently and consistently hot enough to kill all pathogens.

It would be a lot of effort to run a separate pile just for this purpose unless you are really serious about working with your dog’s poo– and if you are I do not mean to stop you– but if you are only managing one pile and want to add food scraps and use it on your garden then I would leave the dog poo out.

Have these questions and answers been helpful to you? We’ve still got a few more interesting issues in composting to look at, at the end of April. If you have any questions that we haven’t answered yet, feel free to ask them in the comments.