Isn’t it surprising how much we take for granted? Consider alternative daily cover (ADC). For many landfills, ADC is so much a part of the operation that it has become the “default” cover method. But there are still many landfills not using ADC in any form or fashion.
Why not? Well, perhaps they just aren¹t sure that it¹s the right thing to do. Or maybe it¹s just too difficult to change. After all, old traditions die hard.
About half a millennium ago, lots of folks were sitting on the seashore, debating whether or not the world was flat. While they were talking, a group of daring explorers was busy sailing around the globe, laying claim to vast new territories. Despite their good intentions, those guys on the beach sort of missed the boat.
Even today, lots of folks are sitting at their landfills, debating whether or not ADC can save airspace and money. While they¹re busy talking, a new generation of daring landfill managers is discovering that the benefits of ADC go far beyond just saving dirt and money. With a host of ADC opportunities continually being discovered, are you expanding your horizon … or just sitting on the beach?
Landfills that aren¹t using ADC, or that are simply using it because it saves dirt, might be missing out on some other benefits.
Saving dirt and money is important – very important. But the fact is that ADC can boost revenue and add lots of flexibility to any landfill¹s operation. Many landfills have gained approval of a variety of ADC materials, allowing them to pick and choose as the situation requires.
Sure, we know that at most landfills ADC will save soil, airspace, and money, but what else can it do? Plenty. Generates Additional Revenue. There are two sides to the profit picture: revenue and expenses. Much of the excitement about ADC hovers around its ability to reduce costs. But in some cases, it can actually cross the line and boost revenue.
In many areas, MSW goes into lined landfills and other (inert) materials go into construction and demolition (C&D) landfills. Why? Because the C&D landfills typically offer lower tipping fees.
Why would a lined landfill want to fill up any of its valuable airspace with inert material for which it might only receive a few bucks of revenue? Perhaps so it wouldn¹t have to spend money for cover soil or a manufactured ADC product.
Hey, if you¹re going to use some kind of inert material as daily cover, what is better: to list it as an expense or as income? Lots of landfills are spending piles of money on ADC. But an increasing number are, in effect, finding ways to get paid to use ADC.
Think about the possibilities. In every region, there are a variety of materials that a landfill might be able to use as ADC and make a little revenue in the process. Here¹s a partial list of materials that have been approved as ADC:
- petroleum-contaminated soil
- shredded tires
- auto shredder fluff
- biosolids
- ash
- cement kiln waste
- dredge spoils
- foundry sand
- oil production waste
- shredded greenwaste
- composted MSW (3/8 in. minus)
- shredded woodwaste
- compost-pile reject
- asphalt/concrete rubble
There are, in fact, scores of different materials approved for use as ADC. The key here is that many of these materials previously have been considered problem wastes–things that couldn’t generate enough revenue to compensate for the landfill space they consume.
It’s like looking at that same old flat world and suddenly realizing, “By golly, that thing might just be round after all!” Sort of puts a new spin on ADC, eh?
Flexibility. There’s more than one way to skin a cat, so to speak. And when it comes to covering the garbage at the end of the day, flexibility is a good thing. How many times have you seen a situation where you couldn’t cover with soil because it was too muddy, the soil was frozen, the scraper broke down, the crew was short-handed, the truckers that import soil were on strike, or … ? You fill in the blank.
And don’t think that cover problems are limited only to soil. Traditional types of ADC can also be impacted. Have you ever heard: “It snowed on my tarp and I can’t pick it up,” “My tarp blew away,” “It’s too windy to use foam,” “The ADC machine is down”?
Please don’t misunderstand. I’m not down on traditional types of ADC. Tarps, foam, film, and so on all play a vital role in the landfill industry. The point is that there is no one type of ADC that works best at every landfill, every day. When it comes to landfills, things change–sometimes daily. A landfill manager must be able to go with the flow.
| Stockpiled ADC |
So when it comes to ADC, don’t get locked into one method or a specific type. Be mindful of your landfill’s changing conditions and needs. Such things as variation in the amount or type of waste you receive, weather changes, cost, regulatory acceptance, dependability, and material availability are important considerations.
In many states and provinces (perhaps all of them), to begin using a specific type of ADC, a landfill must first show that the proposed ADC material will satisfy the regulatory standards. This often means conducting a short pilot program. If you’re going through the effort of putting together a proposal, it makes sense to include as many options as possible. Again, focus your effort on what makes sense for your landfill.
Keep in mind that regulatory or economic changes might impact a certain material or type of ADC. Having the ability to adjust quickly to unexpected changes can be crucial.
A small landfill in central California with approximately five years of remaining life uses a combination of ground woodwaste, ground greenwaste, and some unground woodwaste. Historically it also has used tarps. The landfill’s choice is based on economics and performance. Here’s a rundown on what it’s doing and why.
Unground Woodwaste. On a short-term basis, this landfill finds that it’s hard to beat unground woodwaste and greenwaste. There’s no capital cost. The woodwaste simply is placed on the slope and compacted. On the downside, it takes considerably more than 6 in. to provide adequate daily cover. Thus, while the short-term cost is low, when airspace is factored in, the long-term costs are significant.
Ground Woodwaste and Greenwaste. Ground wood and greenwaste are also used as ADC. While it costs more than unground woodwaste, the ground material is easier to place and can be placed in thinner lifts¾ 6-12 in. As an added benefit, during the wet season, ground woodwaste and greenwaste provide a good driving surface at considerably less cost than gravel.
Tarps. Historically this landfill has used tarps. Although they were effective, the expense of buying and replacing the tarps has led this landfill to stop using them.
Example 2: Medium-Size Landfill
A medium-size regional landfill in the Pacific Northwest uses four types of ADC. This particular site has little soil available on-site, so the ability to use ADC every day is vital. Why would a medium-size landfill want four types of ADC in its repertoire? Flexibility.
Wood Chips. In the past, this landfill used wood chips. Because of its location, lumber-mill waste, in the form of wood chips, has provided a readily available ADC material. However, recently developed new markets for the wood chips have increased their cost from free to $10/ton. As a result, the landfill will move away from the use of wood chips.
Film. This landfill recently purchased a dozer-mounted system from EPI for placing film as ADC. This will fill the void left by the loss of wood chips as inexpensive ADC. The cost is slightly more than $0.02/ft.2 (excluding the capital cost of the machine).
Petroleum-Contaminated Soil. Used only during the summer months when runoff isn’t an issue, petroleum-contaminated soil (PCS) is one of those waste materials that can double as ADC. But because it is generated by cleanups, tank pulls, and so on, availability is not always reliable. On the upside, PCS generates revenue, not expense.
Plastic Tarps. This landfill also makes extensive use of 12- to 20-mil plastic tarps. These are placed using a combination of equipment and hand-pulling. Material costs range from approximately $0.08 to $0.16/ft.2 They offer the advantage of durability and good protection from infiltration, but the cost is somewhat higher than the other options.
| Tarping conserves airspace and soil and can be applied quickly. |
Sacramento County, CA’s Kiefer Landfill receives approximately 2,000 tpd. A traditional landfill in many ways, it uses both manufactured ADC and waste material for cover.
Tarp-O-Matic. The Kiefer Landfill’s primary ADC system is based on Tarp-O-Matic’s mechanical tarping system. This system was selected because it conserves airspace and soil and because of its low cost and ability to be applied quickly.
Shredded Tires. With zero cost, shredded tires conserve space and help solve the problem of what to do with waste tires. Shredded tires are applied with the dozer.
Composted MSW (3/8 in. minus). Another zero-cost material, composted MSW passing 3/8-in. screen, is used as ADC. Placed with the dozer, this represents the ultimate in recycling: using (composted) garbage to cover garbage. Talk about an efficient refuse-to-soil-cover ratio–it’s all garbage!
Chipped Woodwaste/Greenwaste. Though not used at this time, the Kiefer Landfill might begin using chipped woodwaste/greenwaste within the next few months.
According to Assistant District Manager Bill Gilmour, the Altamont Landfill in Livermore, CA, can select from six different ADC materials. Its choice of ADC is based on site conditions. At 7,000 tpd, the active area is large and moves quickly. This requires a dependable, amply sized source of ADC. Also, the landfill receives consistent high winds (as evidenced by thousands of wind turbines on nearby hills). For this reason, tarps and foam aren’t practical. So what kind of ADC does a windy megalandfill use?
Petroleum-Contaminated Soil. Similar to many other landfills, the Altamont Landfill uses PCS. Used not only as ADC, it also aids in the construction of temporary roads and the touching up of areas of skimpy cover. It not only generates revenue, it also is easily placed with the dozer.
Biosolids. Who wants biosolids? Landfills that know the value of this material for ADC, that’s who. Biosolids are often a revenue producer for landfills. Sometimes the landfill uses biosolids as ADC because there’s no other practical use for the material. In any event, if used properly, biosolids can be an efficient and dependable source of ADC material.
Shredded Tires. With its pilot program approved, the Altamont Landfill is not yet using shredded tires for ADC, but it’s an option that’s available.
Auto Shredder Waste. Auto shredder waste is another one of those waste materials that can generate revenue and function as ADC. This material, which is spread with the dozer, arrives in semi-end dump trucks and, during dry weather, can be dumped wherever it’s needed.
Greenwaste. Greenwaste is a readily available material. Used alone or combined with biosolids, it is applied by dozer.
Ash. Here’s another so-called waste material that doubles as ADC. It too may be used as is or mixed with biosolids before being placed by the dozer.
| Woodwaste |
Despite the variation in the ADC materials they use, these innovative landfills all have one thing in common: They’re using whatever materials are available to save airspace, cut costs, and bring maximum flexibility to the operation.
Whether your ADC arsenal includes peashooters or canons, the key is flexibility. Select materials based on reliability, dependability, effectiveness, cost (or revenue), and regulatory acceptance.
Use common sense. Look at it from all the angles. Obviously nobody would use asbestos as ADC. Sure, its fire-retardant capabilities are great, but from a worker-safety standpoint, it wouldn’t be a good idea. Also, keep in mind that you can get too much of a good thing – that includes ADC.
For example, a landfill that decides to use wood chips for ADC might announce, “We’ll take all the wood chips you have, free.” That’s great, as long as you don’t end up being buried in wood chips. Or having to double and triple handle the chip pile because it’s too big or it’s in the way.
Another pitfall is that when there is a local glut of nontraditional ADC, landfills might use it to excess. I’ve seen situations where a landfill was using 1.5-2 ft. of wood chips as ADC, simply because it was available. The same scenario can exist for any type of ADC. Remember, the primary goal of ADC is to cut costs and save landfill airspace, not just use lots of ADC.
This is not to say that landfills shouldn’t use these materials to great extent, nor should they stop looking for new materials. When it comes to ADC, there are still many discoveries to be made. The point is that you need to have your eyes open. Just because you know the world is round doesn’t mean your ship can’t sink.
When it comes to ADC, you’ve got a lot of alternatives. Learn what they are and how your landfill can benefit from having and using a variety of them.