Composting – The Future for all Restaurateurs

Restaurateurs have an obligation to protect the United States economy and its environment. The “green” word is becoming more and more entrenched within our vocabulary, and you can make a difference, if you will just take a strategic view at how your restaurant group disposes food resources into the waste stream.

Landfills are closing up at alarming rates; because of this, waste disposal and tipping fees are escalating. Here is an interesting fact:  “food waste placed in airtight landfill space stops the earth’s natural cycle of decomposition, plus organic matter tends to react with other materials that create toxic leachate.”  Did you know that more than “72% of all materials entering landfills can be diverted through composting?” In 2007, it has been estimated that more than “16 million tons of food scraps were generated accounting for 10% of the Municipal Solid Waste stream” in this country.

A way to decrease the need for landfill space, improve water quality and cooperate with the agricultural environment is through composting. The reasons to compost are as follows:

• Diverts food waste, yard trimming, cardboard and wood from landfills.
• Accounts for about 30% of Municipal Solid Waste (MSW).
• Provides an alternative to synthetic fertilizers.
• Aerobic composting produces high quality solid and mulch for use at commercial business or consumer use.

How Composting Works:

When setting up the formula, there is a need for the proper nutrient mix, which includes a correct carbon to nitrogen ratio (C:N). Bacteria must be able to process the organic materials into the desired compost. An optimal ratio is 30:1. If there are changes to the ratio, where product is increased at any level, decomposition is slowed. If materials are reduced at any level, nitrogen is released, which is where the foul odors can occur. For purposes of what the food waste industry is looking for there is a need for:  food waste at a 15:1 ratio, leaves at a 60:1 ratio, the bulking agents include:  pallets, cardboard or wood 100:1 and sawdust 500:1.

In order for micro-organisms to breakdown compost, there must be no less than a 60% moisture content. If moisture reaches 70%, it slows down the composting process, and creates foul odors. Moisture content below 50% slows down the decomposition process. Fresh food waste has a moisture content of between 80 to 90%, sawdust has 25%, and yard waste is normally at 70%. When compost has the proper moisture content it will form a clump, being slightly wet to the touch. If the clump drips water, then it is too wet and normally requires additional bulking agents such as sawdust or yard waste.

Oxygen or aeration is vital for optimum micro-organism growth to effectively breakdown the composted matter. This is normally accomplished by turning, mixing, using fans/blowers, aeration holes, or raising the compost off the ground.

Particle size has an affect on the rate of decomposition within the compost pile. If particles are small, more oxygen is produced; therefore, micro-organisms thrive and compost is broken down faster. This is accomplished in the very beginning, before any materials enter the compost pile by grinding, shredding, chipping, chopping, or cutting of all materials.

Types of Composting

1. Passive composting or piling. Stacking of materials and letting them decompose naturally. This method is simple and low cost but is very slow and may result in objectionable odors; not conducive for restaurants.
2. Aerated Static Piles – air is introduced to the stacked pile via perforated pipes and blowers. This method requires no labor to turn compost but is weather sensitive, and can have unreliable pathogen reduction due to imperfect mixing.
3. Windrows – “is the production of compost, by piling organic matter or biodegradable waste, like animal manure and crop residues, in long rows (windrows.) This method is suited to producing large volumes of compost. These piles are generally turned to improve porosity and oxygen content, mix in or remove moisture, and redistribute cooler and hotter portions of the pile. Windrow composting is the most commonly used of farm scale composting methods. Process control parameters include the initial ratios of carbon and nitrogen rich materials, the amount of bulking agents added to assure air porosity, the pile size, moisture content, and turning frequency. This method produces a uniform product and can be remotely located.”  Windrows are typically used for hefty volumes, which normally require a lot of acreage. In addition, windrows can have odor problems, if the materials are not correctly mixed where there may be issues of leachate, if exposed to rainfall.
4. Bins – consist of wire mesh or wooden frames that permit excellent air circulation; they are inexpensive, and require marginal labor. Two/Three chamber bins allow for quicker compost production; however, they can be unstable for decomposition of the materials. Bin composting is typically used for small amounts of food waste; not conducive for restaurants.
5. In-vessel systems – organic materials are fed into a drum, silo, concrete-lined trench, or similar equipment where the environmental conditions – including temperature, moisture, and aeration are closely controlled. The apparatus usually has a mechanism to turn or agitate the materials for proper aeration. In-vessel composters vary in size and capacity.

   In-vessel composting can process large amounts of waste without taking up as much space as the windrow method. In addition, it can accommodate virtually any type of organic waste (e.g., meat, animal manure, bio-solids, food scraps). Some in-vessel composters can fit into a school or restaurant kitchen while others can be as large as a school bus to accommodate large food processing plants.

   In-vessel composting can be used year-round in virtually any climate because the environment is carefully controlled, often by electronic means. This method can be used in extremely cold weather if the equipment is insulated or the processing takes place indoors.”

6. Vermi-composting uses worms to consumer the food waste and utilizes its casting as high quality compost. This is usually done in containers, bins or greenhouses. Typically one pound of worms can eat four pounds of waste per week. Many schools use this type of composting as an environmental education tool. Worm casting bring a premium price, but the investment in worm stocking may be high depending on the size of the operation. If too much waste is added anaerobic conditions may occur. In addition, worms cannot process meat products; not suggested for restaurants.

When is Compost Done?
It will be similar to humus in look, aroma and feel. It will maintain an ambient temperature; thereby, no weed seeds or pathogens will be in the mix. The pH level will be somewhere near 7.0, and the moisture content somewhere between 35 to 50%. The C:N ration will between 10:1 and 25:1; its organic content will be between 40 to 65%. As a mental note, no unfinished or immature compost should be placed onto the ground, for it will contain phytotoxin that kill plants.

Where is it Used?
Restaurant mulch can be used by farmers for field crops, the Forestry service for annual plants, commercial business for sod farms, greenhouse crops and mined lands. On the residential side, composting can be used as mulch for trees, orchards, landscapes, lawns, gardens & makes excellent potting mix. Plus used on golf courses, trails, athletic fields and parks. In some cases, methane, extracted from tented composted areas is used to power facilities.

Who needs to compost?

• Food stores
• Restaurants
• Hospital cafeterias
• Hotel food services
• Food manufacturers
• Food processors
• Education food services

Benefits to the food waste industry:

• Composting fees on a per ton basis are generally half of waste disposal services, depending upon the location.
• Reduces solid waste disposal fees, because you are taking the weight out of the trash container.
• In many municipalities composting is a non-taxable service.
• Markets the restaurant as environmentally conscious.
• Protect natural resources.
• Assists local farmers and the community.
• Reduces the need for more landfill space.

How do you estimate what your business produces in the way of food waste:

• Converting volume to weight.
  • Food waste is estimated at 750 pounds per yard.
  • Solid waste is estimated at 150 pounds per yard.
• Indicators of food waste generation:
  • Do you have the space available to house additional container(s)?
  • Number of plates served.
  • Square footage of your specific property.
  • Number of employees.
  • Amount of solid waste – trash, cardboard and co-mingled waste.
  • Number of customers throughout the month –use an average.
• How much are you throwing away?
  • Formula for solid waste disposal:
  • #of containers times the size times the number of pick ups.
  • Example – restaurant: 1 –(8) yard container picked up 4 x’s/week= 32 yards
  • Average 60% of food waste = 19.2 yards (food waste)

The Future of Composting
As landfill space decreases, costs escalate, and agricultural practices continue to exhaust soils and deplete organic matter, there will be more pressure to compost your food waste. Laws already exist in many states that require counties to compost. Because of this increasing demand, supermarkets, restaurants, and schools, which alone produce over 16 million tons, can be composted today. It is your civic duty to source separate food scrap, and play an important role in agricultural operations, which is also an opportunity for added income. For more information contact SLM – Facility Solutions Nationwide.

Quoted Sources:

1. Wikipedia – windrow composting
2. US Environmental Protection Agency – in vessel composting; summary of Markets for Composts, and Organic Materials Management Strategies.
3. Consumer’s Handbook for Reducing Solid Waste (USEPA)
4. Municipal Solid Waste Generation, Recycling, and Disposal in the United States:  Facts and Figures for 2005 & 2006, (EPA 530-F-06-039 & EPA 530-F-07-030, respectively).