The first and most important thing to know about yardwaste is that there’s a lot of it. The USEPA, which keeps track of such things, asserts that 245.1 million tons of MSW were generated in this country in 2007. Of this, “Organic materials-comprised of yard trimmings, food scraps, and paper and paperboard products-represented more than two-thirds of this MSW. Even if all paper and paperboard products were recycled, the balance that we call yard waste totaled 50 million tons.”
That means that that either we are separating and putting 50 million tons of this organic residue into those green barrels or drop-off-bins or somehow some of it is getting into landfills-as all of it used to. Until about 1990, few people knew or were concerned about the fact that all this vegetative material shouldn’t be conveniently gotten rid of by dumping it into dumps. They knew it smelled bad, yes, but they were unaware that there was a sinister reason for that: in a landfill, vegetative material breaks down into biogas containing large amounts of methane. And methane, we now know, is a major contributor to global warming.
Now, two decades later, most states have banned the landfilling of yardwaste, although there is speculation that some yardwaste and other organic materials still creep into landfills. However, it’s not likely to be too much, since with today’s tipping fees it literally doesn’t pay to sneak yard waste into a landfill. So at considerable inconvenience and expense, we have to source-separate and collect yard waste and somehow dispose of 50 million tons of it every year. So far, we have devised three methods to deal with yard waste.
The first and currently the most popular method is composting. This involves (1) backyard composting, thereby slightly reducing the amount of yard waste that has to be collected, or (2) sending the yard waste to centers where municipalities or professional composting firms compost it either in and of itself or mixed with other waste streams such as food scraps or sludge. Either way, the product is used to produce land cover or marketable compost or mulch. Composting is by far the largest and most widespread (so to speak) use of yardwaste.
There are several reasons for the substantial use of composting. First, it is widely perceived by the public to be a “good” thing to do. Prodded by public service programs such as the EPA’s GreenScapes, and flyers inserted in utility bills, homeowners have become aware of grasscycling (leaving cut grass on their lawns) and backyard composting of food scraps with yard waste with increasingly capable backyard composters. It has been a remarkably effective public information program. In 1990, the EPA estimates, the recovery rate for grasscycling or composting yard waste was just 12%; a decade later, it had grown to 56.9%, and the industry had almost quadrupled to nearly 3,800 facilities. Although the EPA has not published a comparable report for the current decade, it would appear that composting and its industry have continued to grow.
In its landmark 1999 report, Organic Materials Management Strategies, the EPA postulated a bright future for composting, concluding in part that:
- Approximately 36% (75 million tons) of the US MSW stream could be composted
- Approximately 37 million tons of organic source reduction programs (including grasscycling and backyard composting) could be diverted from the waste stream
- Approximately 62 million tons of the available organic waste stream could be targeted by a combination of grasscycling, backyard composting, composting yard trimmings, on-site institutional composting, and commercial composting programs.
- Approximately 28 million tons of leaves, grass, and brush could be composted
- No prediction is made for mixed-waste composting because of public opposition and technical difficulties
- No prediction is made for residential source-separated compost programs which include food scraps, soiled paper, and yard trimmings although “source-separated composting programs might offer a viable alternative for capturing a significant percentage of the organic materials that are available for composting but that are not targeted by established strategies or technologies”
The potential market for finished compost is much larger than the potential supply. If all applicable materials listed above were captured for composting, approximately 48 million cubic yards (37.4 million tons) of finished compost would be available each year to supply a market potential of more than 1 billion cubic yards of finished compost.
Well, the picture today isn’t that bright, although significant strides have been made. For example, that sixth prediction (really a waffle) has become a reality in cities in the Netherlands, Germany, Switzerland, and in the US, most notably in San Francisco. The City has been successfully co-composting greenwaste and food waste to produce a marketable product in high demand, particularly by nearby vineyards, which take about 90% of the dual-material compost with its high levels of nitrogen and other nutrients to recondition their soil after harvest.
Every day, San Francisco and Oakland collect tons of food scraps from chicken bones to coffee grounds-as well as used napkins, milk cartons, and other food-soiled paper-from restaurants, hotels, markets, and coffee shops. This material is trucked to Vacaville CA to Jepson Prairie Organics, a wholly owned subsidiary of Entergy (formerly Norcal Waste Systems Inc.). There, it is combined with yardwaste generated in Vacaville and nearby Dixon and co-composted. Presently, Jepson processes approximately 5,200 tons of food scraps and 2,000 tons of yardwaste each month. The two feedstocks are fed into an industrial sized grinder, mixed to the proper blend, and pushed into an Ag-Bag composter which features a 200-foot plastic pod equipped with a forced aeration system. After 60 days, the compost is laid out in windrows, which cure the compost for another 30 days. After it is separated in trammels, the finished compost is ready for bagging or bulk delivery.
San Francisco is so sold on this program that a law to require residents to separate and recycle yard waste and food scraps for composting is expected to be approved by the end of this year. This will be a unique step. While Seattle, San Diego, and Philadelphia have mandatory recycling laws in effect, San Francisco will be the first to introduce mandatory composting.
To prepare for the expected increase in recycling materials for composting that will result from the new law, San Francisco’s garbage companies have developed a facility exclusively for handling food scrap and yard waste. Route trucks will collect compostable materials from green carts at 75,000 homes and about 2,100 food outlets. The material will then be off-loaded onto long-haul trailers that will deliver it to the compost facilities. No compostable or recyclable materials will be accepted at any of the city’s transfer stations.
This program will be another significant step toward San Francisco’s goal to achieve zero-waste landfilling by 2020. Already, the city has achieved the highest recycling rate in the country by diverting 70% of its MSW from landfills, and city officials predict that the new mandatory program will enable it to reach 75% by 2010.
However, the composting picture nationwide hasn’t been as rosy as the EPA predicted a decade ago. It would seem that the primary financial value of composting is just that composting costs less than tipping charges at a landfill. And it appears that some states are experiencing a glut of compost and mulch because it greatly exceeds market demands. Edward Lee, vice president of Consolidated Resources Recovery (CRR) in Sarasota FL, described this situation in no uncertain terms in a letter that he sent last summer to the Florida EPA, urging extended land application of processed yard waste. It said, in part:
“The fact is that there are not sufficient markets in Florida to absorb all the processed yard waste and land clearing debris that is currently being generated by City/County facilities, private facilities, and land clearing operations all competing to move biomass off their site at the lowest cost.. The fact is that there are presently millions of tons of mulched yard waste and mulched land clearing material sitting in massive piles at yard waste facilities, landfills, and private unpermitted property throughout Florida today; all the owners of these piles are dreaming of the day when it has value because they can’t afford to get rid of it…
…”I think that anyone producing or selling compost in today’s economic slowdown (August 2008) will tell you that the product will be worth less than zero if you attempted to add millions of cubic yards to the market. The fact is that there is not sufficient market demand for millions of cubic yards of additional compost in Florida; that’s 25,000,000 more 2-cubic foot bags to sell at Home Depot and Lowes per year. If composed yardwaste were of any real value, net of freight and processing costs, then the mountains of stockpiled mulch sitting at dozens of failing or failed yard waste processing facilities throughout Florida (millions of tons) would be screened and sold…[I]f some consultant tells you that we can all just compost our way out of our yardwaste disposal issues then they should be able to answer why our state has millions of tons of already composted yardwaste sitting in static piles presently with no buyers. Ask the city of Jacksonville how much interest they have received in marketing their 80,000–100,000 tons of 3-year-old processed and unprocessed waste piles sitting on 57 acres. It will cost Jacksonville millions of dollars to have this material marketed to some form of beneficial use offsite. Ask Broward County how successful they have been in marketing their now 4-year-old accumulation (35,000 tons) of decomposing waste that they can’t even get the contractor they hired to dispose of it, to haul it off since starting last year.
“Again, the monetary value of processed mulch has no relevance to the fact of its eventual beneficial use whether it is land application, fuel for electric generation, or potting soil for the homeowner.”
Of course things may not be quite as dire as this elsewhere in the country. After all, this is Florida with perhaps the nation’s greatest vegetative growth (estimated to be 10% of the entire US total) and hence certainly its largest amount of yard waste to deal with. Pat Byers of the Solid Waste Authority of Florida’s Palm Beach County, explains, “Once you get south of Orlando, it’s a totally different vegetation than it is in the rest of the state and the country. There’s just so much of it, and it grows so fast that it’s very difficult to keep up with it.
“Our Solid Waste Authority has responsibility for recycling all the yard waste for the entire county. Most of what we’re doing with yard waste here is grinding it up, screening it, and using it as a bulking agent or as an amendment for waste water sludge composting. As recently as 15 years ago, there weren’t many options. Then, we looked at co-composting the sludge and yard waste. We got together with the largest local wastewater facility in the county and started co-composting. Today, this is a very good facility; we never have had any problems meeting regulations.
“That’s mainly what we’re doing with yard waste today, but there are also three other applications too. For one thing, we do take a portion of our yard waste and use it to make compost. Second, we are land-applying processed yard waste in the Everglades area where the sugar cane is. There’s not a lot of this going on, though; it’s mainly to handle overflow if we’re not doing anything else with yard waste. Third, a portion of the yard waste goes to a co-gen plant that burns it with bagasse and woody waste.
“We don’t burn yard waste ourselves; we just supply it to the co-gen plant operator as feed stock. However when we complete our new waste-to-energy plant (it will be the second one in the county), we will have about a 5000 tpd capacity. At that time we’re going to need a lot of yard waste so we’ll send it there to generate energy, rather than provide it to the land application people. In about five years, then, a sizeable percentage of our yard waste will be going there.”
The second significant method of disposing of yard waste is to use it as feedstock to waste-to-energy (WTE) facilities. The WTE industry has been enjoying a resurgence of acceptance as they overcome NIMBY objections that have been based on pollution and odor concerns. Now, these problems have little basis in fact. The US EPA now states that waste-to-energy plants produce electricity with “less impact on the environment than almost any other source of electricity… Modern waste-to-energy facilities meet or exceed EPA’s Maximum Achievable Control Technology (MACT) standards. Today’s waste-to-energy facilities are designed and operated to produce nearly complete combustion of waste and emit low amounts of pollutants. Waste-to-energy destroys pathogens, organics, and other disease-bearing material in trash.”
Nor is the WTE industry now plagued with charges that WTE operations compete with recycling to the detriment of recycling. Eileen Brettler Berenyi’s 2009 update of her Recycling and Waste-to-Energy: Are They Compatible? report should put that shibboleth to rest. The report concluded that, based on a survey of 82 WTE facilities and 567 local governments in 22 states, “Communities nationwide using WTE have an aggregate recycling rate at least five percentage points above the national recycling average.”
Today, about 10% of America’s garbage is disposed in these plants. In 2008, according to the Integrated Waste Services Associates, there were 87 WTE facilities in the US, and they generated more than 2700 megawatts of electricity, enough to power 1.7 million homes.
The question remains, however, whether the typical stream of sorted yard waste from green barrels is a useful fuel for WTE facilities. Robbie Gill of Cloverdale Fuel in Langley BC is dubious, and his Darmon Recycling Group accepts and has experience in waste reduction and disposal of yard waste, as well as brush, stumps, and wood slabs.
“Yard waste is certainly a component of the feedstock we provide,” he says. “But yard waste as an exclusive feed stock for efficient incineration? No. You could set up a boiler to handle it, but because of the moisture content, it would not be an ideal fuel. You’d have to supplement yard waste with something else, as we do, to make sure it will burn well in the boiler.”
At the Darmon yard, they blend yard waste with a lot of things – mainly construction debris, brush, and stumps-and these things don’t come in green barrels. They get them from people trying to get rid of them without having to take them to a transfer station or a MRF. Mainly they use yard waste for composting a product that can be sold and placed around plants and small trees.
Jerry Morey of Bandit of Remus, MI also doubts that run-of-the-mill (so to speak) yard waste will be used as a feedstock for waste-to-energy applications because it would take additional energy to dry out the materials to reduce the moisture content from 15% to 12%. However, he points to an operator in Krakow, Poland that is using the Bandit “Beast” grinder to process grass into biomass fuel. These grasses, which have not been dried in advance, are being used by a cellulose paper plant in Swiecie, Poland to fire a boiler that supplies steam and electricity to the plant.
Another power plant in Poland, this one in Opele, had a large supply of wet straw that could not be processed. Another Bandit Beast was able to grind the wet straw efficiently at a rate of 12-14 tons per hour. The ground straw was then fed to the power plant where it too was used to fire a boiler. While baled wet straw and grasses are certainly not quite the same as the typical yard waste in the green barrels provided by U.S. municipalities, the results in Poland do indicate that at least some of the problems with incinerating yard waste can be solved.
Ethanol and Other Biofuels
Potentially, the third significant use of yard waste may well be to produce ethanol and/or other biofuels. Not so long ago, ethanol was seen as the Holy Grail to solve our dependence on petroleum. After all, it was a renewable product. It could be used in automobiles as a replacement for (some) gasoline. It could be mixed with gasoline to any percentage. It had a higher octane than gasoline, thereby allowing an increase in the engine’s compression rate for increase thermal efficiency. And you could get it from a corn field. What’s not to like?
Federal officials, Midwest farmers, investors, and congress all took this bit in their teeth and ran with it. The federal officials trumpeted the potential of corn ethanol as a substitute for increasingly expensive gasoline and an increasingly risky dependence on foreign oil. Farmers rushed to plant more and more corn at the expense of other food products. Investors took the plunge and spurred the development of corn ethanol refineries. And Congress blessed them all by mandating an increase of biofuel (AKA corn ethanol) production to peak at 6,000,000,000 gallons a year. Hallelujah, we are saved, and we’re all going to be rich.
But then, pesky researchers started to peer more closely at corn ethanol. Some calculated that the energy expended in the planting, shipping, refining, and mixing corn ethanol exceeded the energy savings 15% of gasoline would offer. And to rub salt in the wound, they added that corn ethanol production would actually increase global warming.
Other malcontents did the math and calculated that converting the entire US grain harvest would only produce 16% of this nation’s automobile fuel needs. They then speculated that competing with food markets for agricultural land to such an extent would inevitably raise food prices. And so it turned out to be. The prices of corn and other foods did indeed rise and began to be in disturbingly shorter supply.
Then, on May 5, 2009, the Obama administration effectively pulled the plug on corn ethanol. The EPA proposed renewable-fuel standards that almost surely will reduce the $3,000,000,000 annual tax break the previous administration had offered to producers of corn-based ethanol. Specifically, the new EPA standards proposed on that Cinco de Mayo include indirect land-use calculations in predicting emissions. Corn ethanol production will not pass this test easily, if at all. Holy Moses, the jig’s up and we are ruined.
Or are we? Is this the end of ethanol? Almost certainly not. Several non-food crops (such as switchgrass) are being grown specifically for biofuels, and they can both pass the new EPA test and not impact food prices. Brazil has a flourishing ethanol program using bagasse, the fibrous residues remaining after the juices have been sugar cane. Instead of searching for ways to get rid of this residue, they are using it to produce ethanol. And the icing on the cake is that it doesn’t eat into the world’s food supply. A recent World Bank research working paper stodgily concluded that “Brazil’s sugar-based ethanol did not push food prices appreciably.”
The appetite for ethanol continues to be whetted although the more cautious prefer to use the term biofuels. So now the race is on to find one or more biomasses that are renewable (or inexhaustible), are readily available in large quantities, and that do not affect food or other commodity prices appreciably. The immediate assumption is that such a biomass would have to be a single vegetative source like bagasse, or switchgrass, or cassava, or hemp, or used telephone poles. (Yes, there is a new facility being built in Westbury, Quebec that is designed to make ethanol from used telephone poles. I kid you not.)
But is that single-source assumption valid? Couldn’t it be a combination of sources that are routinely collected together and satisfy our basic criteria for ethanol? Like yardwaste, for example? It is certainly inexhaustible; it is readily available in large quantities, and its usage would not affect prices of food-or any other commodity, for that matter. And there are a surprising number of university and entrepreneurial projects, experiments, pilot plants and even a commercial facility or two seeking the new Holy Grail that will make ethanol production a viable contributor to our energy needs. Few of them are specifically targeting yard waste as a feedstock, but their research leads one to believe that yard waste, with all of its advantages, shouldn’t be ruled out.
Perhaps the most interesting of these projects (and perhaps the nearest to commercial status) is being built by Montreal-based Enerkem. (Yes, that’s the same outfit that is determined to make ethanol from used telephone poles or other utility poles.) Enerkem, in a joint effort with Toronto-based Greenfield Ethanol, has received approval to build a $70,000,000 commercial facility in Edmonton, Alberta to turn municipal waste into biofuels.
According to Enerkem’s CEO, Vincent Chormet, the plant will work by using the waste to create synthesis gas. “Then, catalysts will be used to covert the gas into ethanol, methanol, diesel, or a variety of high-value biochemicals such as ascetic acid or acetate. Last year, we entered into a 25-year agreement with the City of Edmonton to build and operate a waste-to-biofuels facility on municipal land and to receive the City’s sorted municipal solid waste as feedstock. The City-which is contributing C$20m to the project-will supply 100,000 tonnes of sorted municipal solid waste that is recycled and composted every year. Construction of the biofuels facility will begin before the end of the year. When completed, the facility will initially produce 9.5 million gallons of ethanol per year, reducing Alberta’s carbon dioxide footprint by more than six million tons over the next 25 years.”
Nor is Enerkem resting. The company also announced that it plans to build a 20-million-gallon-per-year cellulosic ethanol plant in Pontotoc, Miss, presumably using the same technology. The company expects that the $250 million project, which includes the cost of an upstream municipal solid waste recycling and pre-treatment center, will be able to convert about 60% of the trash that comes into the Three Rivers landfill, which handles garbage from seven Mississippi counties. But the Mississippi plant won’t just be running on garbage; it’s also expected to use wood residues from regional forest and agricultural operations, construction and demolition waste, and treated wood.
Enerkem is not the only firm that is betting on using synthesis gas to create ethanol. Bioengineering Resources Inc. (BRI) of Fayetteville, AR stated that it has been developing a synthesis gas fermentation process whereby biomass can be converted to synthesis gas (consisting primarily of carbon monoxide, carbon dioxide, and hydrogen) via a high temperature gasification process. Anerobic bacteria are then used to convert the synthesis gas into ethanol. The BRI process can be used to produce ethanol from cellulosic wastes with high yields and rates. The company explains that this is made possible because BRI has developed bioreactor systems for fermentation that result in retention times of only a few minutes at atmospheric pressure and less than a minute at elevated pressure.
Under a $2.4 million grant from the US DOE, BRI is investigating the feasibility of locating BRI facilities that produce ethanol by processing corn stover next to conventional grain alcohol plants. Corn stover is the other half of the corn plant that remains on the surface aside from the corn kernels. According to Jim Hettenhaus in an interview with the Institute of Local Self-Reliance in 2002, “the stover is 50% stalks, 22% leaves, 15% cob, and 13% husk. Stover does not include the crown and its surface roots. Most of the corn stover is plowed into the soil. Less than 5% is baled for animal bedding and feed. The remainder is left on the surface to retain soil moisture and control soil erosion.
“About one ton of corn stover is produced for every one ton of corn grain. “Corn grain yields per acre have increased by 60% from the early 1970s, from about 85 bushels per acre nationwide to about 135 today. Corn stover yields have increased proportionately. About 250 million dry tons of stover are produced each year.” (This estimate was made before the huge increase brought about by the corn ethanol stampede.)
According to Cincinnati-based engineering firm of Katzen International, “This Corn Stover Project will investigate the production of higher value liquid fuel, ethanol, and by-product power from corn stover. The stover is gasified and the CO, H2, and C02 in the synthesis gas are fermented into ethanol. A single fermentation product, ethanol, is produced and high theoretical yields (140 gallons per ton) are possible since all biomass components, except the ash, are utilized. The purpose of this project is to develop and demonstrate at pilot scale an optimal gasification / fermentation process to utilize corn stover.”
However, Parsons Corp., also heavily involved in this project, is not betting the ranch solely on corn stover. The company is continuing to test various feedstocks, which will lead to the engineering design and construction of BRI’s first commercial plants. These tests involve such feedstocks as wood waste, auto shredding residue and municipal solid waste. So it is certainly possible that yard waste could be a contender.
Not surprisingly, Florida, with its huge amount of vegetation, is actively pursuing the development of ethanol from biomass. Last year, Asjylyn Loder of the St. Petersburg Times, compiled a list of ethanol projects underway in the state. In her article, Loder pointed out that the state had committed $50,000,000 to ethanol projects in 2007 and the first three months of 2008 in the hope that Florida’s ethanol production would reach 200,000,000 gallons by 2017. And exhibiting a touch of irony, she added that the estimated gasoline usage in Florida in 2017 was projected to be 11,900,000,000 gallons.
In all, she determined that as of March 2008 there were nine ongoing ethanol projects in Florida all receiving state grants in 2007 that ranged from $203,130 to $7,000,000. A wide range of feedstocks was being tested. Included were citrus waste, bagasse, woodwaste, sweet sorghum, forestry waste, and sawdust. It is not at all clear how far along any of these processes are. Indeed, it may be a new one starting in 2009 is leading the field.
In January, 2009, Verenium Corporation of Cambridge, MA announced plans to build its first commercial-scale cellulosic ethanol facility to be located in Highland County, FL. In a lengthy press release, the company, which modestly describes itself as “a pioneer in the development of next-generation cellulosic ethanol and high-performance specialty enzymes,” describes next-generation cellulosic ethanol as “a process that utilizes non-food, plant biomass as its feedstock source. The biomass is first broken down into fermentable sugars using acid or enzymatic hydrolysis and industrial enzymes, after which the sugars are fermented into ethanol using various fermentation organisms.”
The company goes on to state that “The plant will be constructed on fallow land, and is expected to produce up to 36 million gallons of cellulosic ethanol per year and provide the region with about 140 full-time jobs, once commercial operations begin. Verenium anticipates breaking ground on this facility in the second half of this year, and expects to start producing fuel in 2011.”
The Highlands County project, which was awarded what seems to be a typical $7,000,000 grant as part of Florida’s “Farm to Fuel” initiative, has some impressive background for this project. Its conversion process originated from the technology developed by a team led by the highly respected Dr. Lonnie Ingram of the University of Florida. Also the company has been operating pilot and demonstration plants in Jennings, LA, where it has been “developing and testing processes to optimize production and lower the cost of cellulosic ethanol.” Moreover, Verenium has entered into a strategic partnership with BP (nee British Petroleum). This international energy company is a big gun that has both technical savvy and deep pockets, a combination which may be very helpful for Verenium in speeding the development and exploitation of its cellulosic ethanol technology. The company has publicly announced that “Verenium and BP are currently focusing on a second phase of collaboration surrounding the development and deployment of commercial-scale cellulosic ethanol production facilities.”
Another serious contender for affordable biofuels may be emerging from down under. In Australia, Dr Steven Loffler of the CSIRO’s Energy Transformed division and colleagues from Monash University in Melbourne have created a process they call the Furafuel Process which produces a stable bio-crude oil from lignocellulose found in green waste such as waste paper, garden waste, crop residues and forest thinnings. As reported by writer Sue Cartledge, the biocrude oil can then be further refined to produce high value chemicals and biofuels, including both gasoline and diesel replacement fuels.
Dr Loffler claims that by making changes to the chemical process of breaking down the constituents of plant-based waste, “we’ve been able to create a concentrated bio-crude which is much more stable than that achieved elsewhere in the world. This makes it practical and economical to produce bio-crude in local areas for transport to a central refinery, overcoming the high costs and greenhouse gas emissions otherwise involved in transporting bulky green wastes over long distances.”
In effect, the researchers are targeting forest thinnings, crop residues, waste paper, and garden waste, which are, of course, the basic elements of yard waste that are typically being separated and collected at curbsides in many communities. These elements contain lignocellulose, which is renewable and potentially greenhouse gas-neutral. Dr. Loffler regards bio-crude as an interim fuel usefully employing easily available waste until alternative fuels can be developed.
CSIRO’s Furafel process is currently being tested at the University of Massachusetts in Amherst. Although the Furafel method of producing biocrude from lignocellulose has been validated in small-scale tests, Dr. Loffler says he has not yet developed a commercially viable method. He plans to patent the Furafel process and then work with commercial partners to develop onsite converter equipment for waste recyclers, local government authorities, and independent refiners.
There really aren’t any conclusions that can be validly stated. However, it appears that this nation is slowly but surely realizing the need for renewable energy sources and a significant reduction in carbon and air pollution. If so, perhaps there will be a stimulus to stop pigeon-holing yard waste as just trash and thinking of the potential of this 50 million to 75 million tons as a potentially invaluable asset rather than as an expensive liability. We have gone beyond just keeping yard waste out of landfills. That’s a done deal, albeit a very useful one. Now, we should be focusing our ever-advancing technology on taking advantage of all of our potential assets, even if they only can be found in a green barrel.