Top Bulking Agents Used For Composting Of Biosolids



The constant companion of the methods of composting of biosolids is the bulking agent. Though many compost experts and environmentalists frown at the use of bulking agents, there’s no getting around it. Without bulking agents, the wastewater solids will turn into a mushy pile of unusable garbage. Not to mention, the foul odor is unbearable.

Bulking agents are usually the be-all and end-all of a compost pile. If there is a problem with the pile, you can usually pinpoint to the bulking agent as the culprit, or you can use the bulking agent to solve the problem. A bulking agent is a carbon-based material that functions to add structure or bulk to your compost pile. The most commonly used bulking agents are these:

  • Agricultural by-products such as manure and bedding from various animals, animal mortalities, and crop residues.
  • Yard trimmings, including grass clippings, tree prunings, weeds, twigs, stumps, leaves, Christmas trees, and other vegetative matter.
  • Food by-products such as coffee grounds, egg shells, rotten vegetables and fruits, peanut hulls, and fish residues.
  • Industrial by-products of wood processing, brewery and pharmaceuticals, and forestry. Other materials that can be used are biodegradable packaging materials, paper mill residues, and paper goods.
  • Municipal solid waste.

For the last item, it is important to note that municipal solid waste cannot be used in a compost pile directly. Rather, these are treated and put under a process that will separate and remove non-biodegradable items such as plastics, glass, and certain paper goods.

How would you know that a compost pile has bulking agents? It is very simple. Bulking agents remove the intense foul odor produced by wastewater solids and food waste. To understand it better, you can do a little experiment. Fill a trash can with food waste and wait for a few days. You will notice that after a few days, the trash can will smell horribly that you cannot even go near it. This is what happens when there is no bulking agent. The food waste will simply turn into an imaginable porridge-like material.

If you add a bulking agent to the can of food waste, that will produce a manageable composting process. Rotting food and even other garbage will still stink, but they somewhat become bearable when you mix in a bulking agent. The addition of bulking agent switches the compost pile from anaerobic decomposition to aerobic composition. Aerobic composition does not smell pleasant, but it’s bearable and sometimes can smell like food. Anaerobic composition smells completely unforgivable.

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