Thursday, February 16, 2017

How to Make Good Compost

Almost everyone with a backyard garden has a "compost pile." It is a collection of kitchen scraps, plant material, yard waste, lawn clippings, and more. However, it is generally unmanaged and just left to itself. As it turns out, that is not a good recipe for effective compost.

Well-made compost creates a rich humus material that is beneficial for lawns and gardens. Most people have the source materials they need to create their own compost. All it takes is a little knowledge and some work. Good compost provides the following benefits:

  • Soil conditioner: adds nutrients and improves moisture retention
  • Recycles plant and animal waste
  • Introduces beneficial organisms to the soil that will: improve soil aeration, bread down organic matter, protect against plant diseases
  • Good for environment – a natural alternative to chemical fertilizers and pest control
For a more in-depth understanding of how a compost pile works, check out the videos on our web site!

Compost materials

Compost can be made from almost any organic material, though proportions do make a difference. Different materials contribute either carbon or nitrogen to your compost mix. The trick is to maintain a healthy working balance between the two elements. As a general rule, you want 2/3 carbon (brown and/or dry) to 1/3 nitrogen (greens). Some common materials are shown in the table below:
Table scrapsNitrogenAdd with dry carbon items
Fruit and vegetable scrapsNitrogenAdd with dry carbon items
EggshellsNeutralBest when crushed
LeavesCarbonBreak down faster when shredded
Grass clippingsNitrogenAdd in thin layers to prevent matting and clumping
Garden plantsNitrogenUse only disease-free plants
Lawn and garden weedsNitrogenUse only weeds that have not yet gone to seed
Shrub pruningsCarbonWoody prunings are slow to break down – shred
Straw or hayCarbonStraw is best; hay (with seeds) is less ideal
Green comfrey leavesNitrogenExcellent compost “activator”
Pine needlesCarbonAcidic, use in moderate amounts
Flowers and cuttingsNitrogenChop up any long, woody stems
Seaweed and kelpNitrogenApply in thin layers, good source for trace elements
Wood ashCarbonOnly use ash from clean materials, sprinkle lightly
Chicken manureNitrogenExcellent compost “activator”
Coffee groundsNitrogenFilters may also be included
Tea leavesNitrogenLoose or in bags
NewspaperCarbonAvoid using glossy paper and colored inks
Shredded paperCarbonAvoid using glossy paper and colored inks
CardboardCarbonShred material to avoid matting
Corn cobs, stalksCarbonSlow to decompose, best if chopped up
Dryer lintCarbonBest if from natural fibers
Sawdust pelletsCarbonHigh carbon levels, add in layers to avoid clumping
Wood chips/pelletsCarbonHigh carbon levels, use sparingly

Preparing your compost pile

It is always best to start your compost pile on bare soil. The soil provides drainage and the natural microbes and earthworms in the soil will migrate into the compost pile, speeding decomposition and proliferating the beneficial microorganisms. The site should have a slight 3-5% slope which assists with the drainage of excess water. You want your pile wet, but not saturated.

The size of your pile depends on the volume of materials you have to work with. A small garden compost pile can be whatever size you need, but a large-volume farming operation, with lots of material, will need to restrain the dimensions in order to maximize the composting process. A large-scale compost pile should be no wider than 10 feet at the base and no taller than 5 feet at the top (center).

Building your compost pile

The components of the compost pile are important, but so is the order of their application. Build your compost pile in layers.

  1. At the bottom of the pile, put your dry, carbon-rich fiber such as hay, straw, fodder, and dried leaves.
  2. Next add your organic matter such as yard waste, stall manure, or saw dust.
  3. On top of the organic material, put your wet layer; kitchen waste, processed materials. Keep this layer thin to prevent the development of anaerobic conditions.
  4. Next add enough clay or mineral sources to make up about 10% of the total volume. This can be clay, soft rock phosphate, humates, or other mineral-rich materials.
  5. On top of the clay is the fresh green materials such as grass, weeds, or green leaves; no more than 5% of the total volume.
  6. Finally, the top layer is between 2-20 lbs of mineral rock dust per yard of raw materials.

Once you have built your pile we recommend adding enough liquid to bring the moisture level up to around 50% (you should be able to squeeze a few drops out of a handful of compost). Be sure to use non-chlorinated water as chlorine will kill the microbial activity in the compost. Always inoculate the compost with Bio Minerals Technologies’ compost/mineral tea to jump-start the microbial population as you moisturize the compost.

Once your pile is built, you need to cover it. It doesn’t really matter what you cover it with: plastic sheeting, wood, carpet scraps. The objective is to retain moisture and heat, both essential for the composting process. The covering can also prevent the compost from being over-watered by rain, giving you some control over the moisture levels in rainy regions.

Maintaining your compost pile

As the pile decomposes, it will generate heat and use up moisture. Some heat is good, too much heat is not. Also, if you lose too much moisture, the decomposition process will slow down and eventually stop, so you need to maintain the moisture level. If you are in a region with regular rainfall, the rain can replenish the moisture. If you are in a more arid region, you will have to add moisture at regular intervals to maintain the proper balance.

Temperature and turning

As the composting process begins, the interior of the pile heats up. The maximum interior temperature at the center of the pile should be no more than 160 degrees F. When the center temperature reaches 150 degrees, you should turn the compost. Turning should drop the temperature by at least 20 degrees.

Constant temperatures above 137 degrees for 10-14 days will kill any weed seeds in your compost.
Turning is a good time to add moisture, if it is needed, as the process of turning will distribute the moisture throughout the pile. If you are turning by hand, just use a pitchfork or shovel.

The highest temperatures are in the first 2-3 weeks of the breakdown phase. By the time you get to the 4th week, much of the breakdown has occurred and the process slows. Temperatures will drop into the 120-130 degree range for the remainder of the process.


If your initial temperatures are too low and don’t get over the 137-degree threshold, then your pile may need one of three things: oxygen, water, or more green nitrogen-based materials.

The water is easy to check. Take a handful of compost and squeeze it. If you can produce a few drops of water, your moisture level is about right. If the compost is dry, add some water and mix it to distribute throughout the pile.

If the moisture level is good and the temperatures are low, then check your O2 and CO2 levels. If the O2 level is less than 8%, you need to aerate the pile to introduce more oxygen. If the CO2 levels are greater than 8%, you need to aerate the pile and reduce the CO2 concentrations.
If the water and oxygen are good and your temperatures are still low, then you probably need to mix more Nitrogen-based materials into your piles.

Finish indicators

There are several indicators that can tell you when your compost is finished. Taken together, they can accurately tell the story of the decomposition process while giving you the quality indicators you need. A quick list is shown below, followed by more detailed discussion of the individual measurements.

Simple indicators:

pH: > 7 < 8

Mature Temperature: No more than 10 degrees over ambient air temperature

Moisture: 50%

Lab indicators

EC: 1,200-2,500 mS after 6 weeks

rH (Redox): 28-29

CO2: < 3%

NO3: 250-300 ppm (summer), 50-100 ppm (winter)

NH4: < 0.5 ppm (if NH4 is > 2% there was insufficient oxygen to complete the nitrogen cycle)

NO2: < 2 ppm in early stages, but 0 in the finishing stages

Sulfides (HS2): None

Organic matter: 12.5 %

Ash: 37.5%

Sodium: < 200 ppm


The pH reading of compost is easily tested with a standard pH meter. To test the pH level of the compost, mix 1 part compost with 1 part distilled water and test with a pH meter.

The pH levels of the compost follow a predictable curve. When the pile is first created the pH will be in the 6s, but it quickly rises that first week to between 8-8.5. If the composting is proceeding properly, it will rise quickly and then decline as shown below:

Week 1: start in 6s and rise to between 8-8.5

Week 2: Peak around 9 and then start dropping back to 8.5

Week 3: Slow decline down to 8.2 or 8.3

Week 4: Continue decline to 8.1 or 8.2

Week 5: Continue decline to 7.8

Week 6: Level off around 7.5

Finished compost should have a pH reading greater than 7 and less than 8.

Electrical Conductivity (EC)

EC is a measurement of nutrients available in the compost. The greater the nutrient concentration, the higher the electrical conductivity. It is measured with an EC meter. The reading should be between 1,200 and 2,500 mS after 6 weeks of composting.


rH, or Redox, is a measurement of relative hydrogen that tells you how well your compost supports the beneficial microbial populations (most beneficial soil microbes are aerobes, which means they require oxygen). The range is from 0-40, with 28 being the midpoint or balance. A score below 28 indicates an oxygen reductive state which is not conducive to beneficial aerobic microbes. A score above 28 indicates an oxidative state which is supportive of beneficial microbial growth.

Redox is calculated with the following formula:

(210 + ORP + 2(pH))/30 = rH (Redox)

ORP = Oxygen Reduction Potential and is measured with an ORP meter. The readings are in mV.

For example, an ORP reading of +250 mV with a pH reading of 7.8 will calculate as follows:

(210 + 250 + 2(7.8))/30 = (460/30) + 15.6 = 30.93

This indicates an oxidizing state that supports beneficial microbial growth.