INTRODUCTION
A. Leaves and Yard Trimmings
Leaves differ from much other municipal solid waste (MSW) in that they occur seasonally and are collected separately. In season, leaves may account for over half the municipal solid waste collected and on a yearly basis may comprise 5% to 30% of the total municipal solid waste stream.
Because separated leaves are homogeneous, seasonal, and usually nonÄobnoxious, they lend themselves to treatment by relatively uncomplicated composting procedures. The end product of the process is compost, which can benefit soils as an organic amendment.
The objectives of leaf composting as a waste treatment process are a reduction in the mass and volume of the starting material and the destruction of putrescible (odor-causing) substances. For compost production, reduction of the carbon to nitrogen ratio (see Section III.F) and elimination of weed seeds and any plant pathogens also are desirable. As cost effectiveness is always a primary concern, the economic and other advantages of composting leaves are dramatic when compared to many alternative strategies.
Other yard wastes in New Jersey include mainly grass clippings and woody materials such as tree trimmings. Grass clippings may account for 10-20% of the total MSW stream, and woody materials perhaps half that amount. In many cases these historically have not been collected separately. Woody materials degrade too slowly to be amenable to composting, and grass clippings, although readily compostable, are problematic at leaf composting facilities. Recycling of both materials will be discussed further below, particularly in Section VI.
B. Current Management Alternatives
According to the New Jersey Statewide Mandatory Source Separation and Recycling Act (P.L. 1987, c.102, or NJSA 13:1E-99.11 et seq.), leaves must be source separated and recycled. Leaves can be recycled by being composted in the backyard, composted at vegetative or leaf composting facilities, or mixed (sometimes called "mulched") into the soil at land deemed actively devoted to agricultural or horticultural use. Grass clippings also may be included at specially permitted vegetative composting sites, and perhaps soon at mulching sites. The regulations for these practices are available through the New Jersey Department of Environmental Protection and Energy (NJDEPE) Division of Solid Waste Management (DSWM), Bureau of Resource Recovery Engineering (addresses and phone numbers are provided in Appendix D; also see Section IV.A). The state does not regulate backyard composting activities.
Leaf composting requires separated leaf collection. This potentially imposes additional collection costs, but already is commonplace. An economic analysis of leaf composting is provided in a separate addendum by Dr. Donn A. Derr.
1. Source Reduction
**[Sentence or two from Ellen]**
a. Backyard Composting
Backyard and municipal-scale leaf composting are complementary activities. Municipalities should encourage backyard composting as a part of their overall yard waste management program. All municipal collection, processing, and distribution costs are avoided for leaves and yard trimmings that are composted by residents. Additionally, other materials such as grass clippings and fruit and vegetable scraps can be included in backyard composting, thus reducing handling of these wastes by the municipality as well.
The backyard composting process is similar to a municipal program on a smaller scale. Leaves and yard trimmings are placed in a free-standing pile or contained in a holding or turning unit. The material is turned manually to accelerate the process and allow for the surface layer to be mixed in and undergo the composting process. The compost produced in this manner can be used to enrich the soil around trees and shrubs and within gardens.
Fact sheet FS 074 on backyard leaf composting, published by Cooperative Extension at Cook College, Rutgers University, is available from county extension offices (in New Jersey) or Cook College (single copy provided in Appendix E). The method recommended in the fact sheet is less complex than those suggested by most others, and was designed to make it easier for residents to get started with composting. However, there are numerous suitable publications available.
b. "Grass: Cut It and Leave It"
Grass clippings are another major component of municipal solid waste. However, they can be easily eliminated from the MSW stream, while at the same time producing a healthier lawn. Leave the clippings on the lawn and let nature do the recycling.
The process is simple. Most New Jersey lawns thrive when mowed to a length of about 2 to 3 inches, especially in summer. To maintain the lawn properly, avoid mowing more than the top third of the grass blades. The clippings will then filter down to the soil, acting as a natural fertilizer. The lawn will be healthier, and the taller grass will shade the soil, cooling roots and limiting weeds.
Lawn experts agree that grass clippings will not contribute to thatch problems. Rather, thatch is formed by the accumulation of dead roots and stems. Increased use of fertilizer and water will cause the lawn to grow faster, resulting in greater thatch build up as well as more clippings.
A copy of a DEPE pamphlet on managing grass clippings is provided in Appendix E. For additional copies, contact your county extension office or recycling coordinator (Appendix D).
c. Backyard Mulching
Another way of recycling leaves, grass clippings, and brush is to apply them to gardens or around shrubs and other plantings as a surface mulch. A one inch layer of mulch can help moderate soil temperatures and reduce weed growth, soil spattering and compaction, erosion, evaporation, and runoff. Brush needs to be chipped first, and leaves also make a better mulch after shredding or composting. All of the materials help improve the organic content of New Jersey soils, although with woody materials this will take a longer time.
2. Composting
For many municipalities, composting has proven to be the best and least expensive method for managing leaves. Over 200 such facilities are operating in New Jersey.
In addition to the cost savings compared to other alternatives, the compost produced has some small monetary value. This may be recognized in reduced purchases of organic matter (such as mulch and top soil) by the municipality, free distribution to residents, and even as product sales. In addition, tonnage grants from the NJDEPE/DSWM can be utilized to help offset composting costs.
From an environmental perspective, composting saves valuable landfill space, avoids the cost and concerns of incineration, and produces compost which can be used to improve soil. Composting of leaves and other yard wastes counts towards the State's 60% recycling targets.
Composting is both an economical and an environmentally sound alternative for handling leaves. However, to fully realize these benefits and to avoid some of the potential problems, care must be exercised in selecting a site and designing and operating the facility.
3. Farmland "Mulching"
Collected leaves also can be "mulched" on land deemed actively devoted to agricultural or horticultural use, as per N.J.A.C. 7:26-1.12 (available from NJDEPE/DSWM). This regulation requires that the operation be included in or consistent with the county's solid waste management plan; leaves be delivered unbagged, and spread onto the field in a thin layer no more than 6 inches deep within 7 days of delivery (no stockpiling for longer periods); and layered leaves be incorporated into the soil no later than the next tillage season.
Pregrinding of the leaves is not required, although it may be beneficial. However, the rate of application for preground leaves should not exceed the rate for unground leaves on a mass (or weight) basis - this means that a thinner layer (probably 2-3 inches) must be used because of the volume reduction.
It may also soon be possible to "mulch" grass clippings. Contact NJDEPE/DSWM for the latest regulations for this practice.
C. "Historic" or Previous Management Strategies
1. Open Burning
For many years, leaves were disposed of by residents through open burning. Prompted by the severe air pollution problems in the state, this practice was banned in New Jersey effective January 1, 1972 (New Jersey Air Pollution Control Code, Chapter 2).
2. Landfilling
Although landfilling is currently a primary disposal method for municipal solid waste in New Jersey, according to the New Jersey Statewide Mandatory Source Separation and Recycling Act (NJSA 13:1E-99.11 et seq.), landfilling is no longer an alternative for managing leaves.
There are numerous reasons for banning leaves from landfills. The siting of new landfills has become extremely difficult, and landfill capacity has decreased sharply. Placing leaves in landfills uses up this limited capacity for a relatively innocuous material, rather than saving it for the more obnoxious fraction of the municipal solid waste stream. As the number of remaining landfills declines, the hauling time and distance increase for many municipalities. Likewise, the waiting time for trucks to dump at some landfills is longer. Landfills also exact a high price in terms of increased maintenance costs for the trucks which ride on them - tires, transmissions, fuel tanks, hydraulic lines, and other components receive hard wear.
Ironically, when leaves were placed in landfills their biodegradability, which makes them suitable for composting, added to the gas, leachate, and settling problems which landfills experience. Thus landfilling of leaves is not only expensive but also environmentally unsound.
3. Incineration
According to NJSA 13:1E-99.11 et seq., leaves are banned from incinerators within this state. Leaves are often too wet to burn well, reducing the potential for energy recovery. On the other hand, when leaves are dry, they tend to be too light and fluffy, adding to the fly ash.
Beyond these problems, incinerating leaves may simply be impractical because of their large volume and highly seasonal nature. Designing a mass burning facility to handle this peak loading may be economically infeasible, since the excess capacity would usually have to be idle for the remainder of the year. For economically sized facilities, peak (as well as down-time) refuse loads have to be diverted to landfills.