Composting is an aerobic process, which means that oxygen is needed for the organic material to decompose. Compost piles need to be turned regularly to create that airflow. People & pitchforks can move small compost piles, but bigger piles need better solutions, systems with air vents & pipes can increase oxygen through the pile, while small tumbler systems can also help to ease the turning process.
In your ventures with compost, you may learn about anaerobic digesters, which are machines created to help break down food without air. This is not considered composting because the end product & process is different, although the goal is still the same.
Compost piles should contain a mix of nitrogen-rich materials (greens) & carbon-rich materials (browns). Greens include any thing that used to be alive such as vegetable & fruit scraps, weeds, coffee grounds, eggshells, meat, dairy, & grass clippings. Browns are things like leaves, straw, mulch, wood products, sawdust, newspaper & shredded paper. A healthy compost pile is generally 50/50 greens to browns; but the ratio depends on what you put in, & your composting method of choice. Chopping your food scraps into smaller pieces will speed up the composting process. Larger pieces will still decompose, but take longer.
Always check the materials your compost program accepts. Most small compost piles don't allow meat, dairy, bones, or greasy items.
Moisture is important to a compost pile; ideally it should feel damp. Being about 50-60% water by weight, a lot of moisture comes from the food scraps. If your pile is dry, you can water the pile, but if you squeeze it and it drips, it's too saturated. You can regulate this with a tarp, enclosed container, or by adding more browns (like leaves, wood chips, or newspaper) to absorb moisture.
Organic matter decomposes faster in higher temperatures, meaning that an active compost pile is warm, even when it's cold out. Turning your compost will generate more heat, although some types of composting may require less heat and mixing than others.
Compost piles are usually hot, anywhere from 110 to 180 degrees Fahrenheit (most organisms cannot survive above 160 degrees). This temperature must be monitored, when it gets too cold (usually around 120 degrees), the pile should be turned. A hot pile is typically turned every 3 to 7 days, and takes 6 weeks to 3 months to decompose into compost. Hot piles also reach high enough temperatures to kill pathogens, weed seeds, & fly larvae.
Compost piles can be cold too, anywhere from 110 to 50 degrees Fahrenheit, this is considered “slow” composting and is lower maintenance. A cold pile can take 6 months to 3 years to finish composting and should not include weeds, meat or dairy. Since the pile doesn’t really need to reach a desired temperature to kill the pathogens in meat and dairy, you can add greens and browns as you collect them.