Making & Using CompostUnit 1.7 | Part 1 – 301
Lecture 1: Making & Using Compost
b) Space needed for composting can take up available production land
c) Odor or other impacts on neighbors can create challenges in urban/suburban areas
d) Rules governing compost production methods must be strictly followed if operating
a certified organic farm (see National Organic Program, http://www.ams.usda.gov/nop for
composting regulations)
C. Biology of the Composting Process
- Compost ecosystem overview
a) What makes composting happen? A wide range of decomposers are naturally present in
most soils and on organic matter. Microbial decomposers can account for 60%–80% of
total soil metabolism. See the discussion and depicition of “Process and Participants” in
Supplement 1 and Appendix 1, Compost Time/Temperature Curve.
b) Decomposer organisms play different roles in a complex compost food web (see
Appendix 2, Compost Food Web). Microscopic organisms such as bacteria, fungi,
actinomycetes, and yeasts are mostly primary consumers of compost materials.
Macroscopic organisms such as mold mites, nematodes, springtails, centipedes, beetles,
and earthworms feed on the primary and secondary consumers.
- Key compost organisms
a) Bacteria are primarily responsible for the first stages of decomposition in the
composting process
i. Feed on succulent plant materials such as simple sugars, plant saps, proteins
and some starches. As their populations can double hourly, the initial rate of
decomposition is rapid.
ii. Use primarily enzymes, manufactured from the N-rich material in the pile, to
decompose the organic matter.
b) Fungi
i. Also decompose simple sugars, plant saps, proteins, and starches, but their primary
role is to decompose the most resistant carbonaceous compounds in the pile, such as
chitin, lignin, and cellulose
ii. Improve soil structure by physically binding soil particles into aggregates
iii. Suppress disease
c) Actinomycetes
i. Filamentous bacteria, some of which grow as segmented hyphae (strands) that
resemble fungi. Actinomycetes give compost its earthy smell.
ii. Produce long, grayish, thready or cobweb-like growths that are most commonly seen
toward the end of the composting process
iii. Can decompose complex carbon, including lignin, chitin and cellulose. Enzymes
enable them to break down woody stems, bark, and newspapers.
iv. Responsible for some disease suppression (produce enzymatic compounds and
antibiotics)
d) Macroorganisms: Earthworm and other later compost pile immigrants (see discussion of
Process and Participants in Supplement 1)
i. Though not always present in finished compost, macroorganisms feed on the pile’s
earlier inhabitants
ii. Examples: Nematodes, mold mites, springtails, wolf spiders, centipedes, sow bugs,
earthworms, ground beetles (for more information, see Unit 2.3, Soil Biology and
Ecology)