Composts What is compost and why use it? What organisms are involved in the composting process? What chemical changes occur during composting? What are the optimal conditions for composting Temperature Moisture Oxygen Does composting kill harmful pathogens (plant and human), nematodes and weed seeds? Safety regulations Compost production systems Small scale Commercial

What is compost – why use it? Composting is the decomposition of plant remains and other once-living materials to make an earthy, dark, crumbly substance that is excellent for adding to houseplants or enriching garden soil. compost improves soil structure, texture, aeration - increases the soil's water-holding capacity. Compost loosens clay soils and helps sandy soils retain water. improves soil fertility and stimulates healthy root development Organic matter provides food for microorganisms - nitrogen, potassium, and phosphorus mineralized

Top 10 Reasons to Compost 10.Be environmentally responsible. 9. Reduce need for chemical fertilizers, mulch. 8. Create a healthy landscape. 7. Improve the quality of your soil. 6. Reduce amount of yard waste going to landfill. 5. Protect the Chesapeake Bay and watershed. 4. Decrease water use in your landscape. 3. Protect privacy. Use shredded personal papers! 2. It's easy. Good exercise. 1. Free bin for Howard County residents! #3 – some kids like to shred their homework – after they get it back from the teacher! Shred old credit card receipts.

The Science of Composting Composting is the natural process in which living organisms decompose organic matter into inorganic matter in the soil. The organisms feed on the organic material and through respiration generate the energy that they use for movement, growth, reproduction or stored energy. The organism excrete inorganic material that enriches the soil. When the organisms die, their bodies add to the organic matter in the compost pile.

+ + + Fresh Organic Materials Oxygen Compost Energy Carbon Dioxide Microbes, Moisture, and Time Compost Energy Carbon Dioxide + + Slide credit: Tom Richard, Penn State University

Organisms use carbon as a source of energy and nitrogen to grow and reproduce. Too little N: there will be few microorganisms, and decomposition will be slow. Too much N: some will turn to ammonia that will volatilize, creating an odor.

Factors affecting the compost process C:N ratio Size and texture Aeration NB. Moisture level also critical

Moisture level is also critical Optimum moisture content 40-60% Feels moist to touch, but when squeezed only produces few drops

Ideal conditions for composting

The Science of Composting: Chemistry Important factors in compost chemistry Oxygen Needed to oxidize carbon for energy Without oxygen will produce rotten egg smell pH Level Acids form as organisms digest organic material and lowers pH Lower pH encourages fungi and the break down of “tough” matter If pH too low (<4.5) limits microorganisms’ activity

The Science of Composting: Physics Important factors for compost physics: Temperature 3 Phases Want to maintain temperature between 55-600C Temperature impacted Heat generated by organism Heat lost to environment through conduction, convection and radiation  shape and size of pile Moisture content (specific heat and heat capacity of water)

The Science of Composting: Physics Important factors for compost physics: Particle size Microorganism activity occurs on surface of organic material The more surface area for organisms to attack, the quicker the decomposition  want smaller particles Flip-side: The smaller the particles, the more dense and compact the material resulting in poor oxygen circulation

The main players Bacteria: major decomposers, breakdown simpler forms of organic material Actinomycetes: degrade complex organics such as cellulose, lignin, chitin, and proteins – earthy” smell, long “spider webs” filaments Fungi: Break down tough debris, too dry, too acidic or too low in nitrogen for bacteria to eat

What do microbes in compost do? Consume organic matter to grow Stabilize organic matter Aerobic oxidation produces CO2 Anaerobic produces reduced compounds organic acids, alcohols Mineralize nutrients Organic to inorganic forms (protein to NH4) Transform nutrients Nitrification – pH and temperature sensitive NOTE: invertebrates not important in high temperature composting, only in cold

Starting your Compost Pile - Ideal size is 3 ft. x 3 ft. x 3 ft. (27 cubic ft.) Easier to turn, aerobic action No larger than 5 x 5 x 5 Can become anaerobic Here are more ideas for creating a workable bin in your yard. Cinder block works well – open side for easier turning. Wooden pallets make a great compost bin too – and allow for air circulation.

Compost production systems Small scale Compost piles need to be at least one cubic to hold the heat from decomposition

Passive composting

Commercial composting Large scale Passive aeration with turning or actively aerated systems

Vermicomposting Vermicomposting is the process of using worms and micro-organisms to turn kitchen waste into a black, earthy-smelling, nutrient-rich humus. The worms used in vermicomposting are called redworms (Eisenia foetida), also know as red wigglers, manure worms, red hybrid or tiger worms. http://lancaster.unl.edu/pest/resources/vermicompost107.shtml

Feedstock conditioning - grinding

Moisture management - most important factor to stabilize biological and chemical properties

Processing – turned windrows

Compost blankets to moderate moisture www.vanierselcompost.com/. ../productie.htm

Composting - windrow CO2 Hot O2 Cool Turning helps aeration and to move material from edge into hot center region CO2 Hot O2 Cool Graphic credit: Tom Richard, Penn State University

Composting – Static forced air Air forces heat outwards Some systems can switch direction to keep base core at high enough temperature Also helps control odor Hot O2 Cool Graphic credit: Tom Richard, Penn State University

Processing - forced aeration

Contain, treat leachate

Compost blankets – beware moving from fresh to curing www.vanierselcompost.com/. ../productie.htm

Cure compost with 40-50% moisture to promote competitive microorganisms and avoid salmonella regrowth