Methods to Handle Organic Waste: Compost and Kilowatts

In 1915, a tragic farm accident reported in The Fruit Grower and Farmer was a mere footnote of local news. Patients from the State Hospital in Athens, OH, whose job was “to tramp down the silage comprised of corn stalks and leaves” were found asphyxiated in a tower silo. The report says “. . . the silage was a little green and had settled about three feet the previous night,” and went on to describe the young men killed by a heavier-than-air gas that so efficiently depletes oxygen that “a lighted lantern lowered in its presence will almost instantly extinguish the flame.”

There was no mention of nitrogen ­dioxide, or carbon dioxide, both lethal byproducts of decaying silage.

A century ago, tower silos were a relatively new structure on the farm landscape. The threat of exposure to this gas from fermenting organic material was an accepted occupational farm hazard. Certainly there was no prediction that this decay of organic matter “anaerobic digesting,” would be a booming business that a century later this process would be induced to purposefully generate biogas as a source of energy to light homes, run tractors, and create heat.

Anaerobic Digestion Overview
The silos that create killer gas are just one example of natural anaerobic digestion (AD)—the consequence of moist plant or manure products decaying in the presence of bacteria to give off a lethal gas product.

In the European Union (EU) anaerobic digesters creating methane gas have long been in operation to comply with EU policies on emission and nutrient management bringing positive environmental and human health results: decreased runoff, less chemical and nutrient deposition from landfills, and reduction of unhealthy incineration emission byproducts.

But AD has flexibility in its technology and depending on the source material, there are two potential outputs—biogas and plant rich residue called digestate.

Ernie Ruckert, an upstate New York-based solid waste consulting specialist with “a professional career in garage,” explains an overview of the process.

“There are two general types of digesters—wet and dry. The ‘wet’ technology is employed at many wastewater treatment plants, where one of the steps in the wastewater treatment process may be an anaerobic treatment tank [Anaerobic Digester] to degrade the organics in the wastewater. Processed organic waste slurry [‘wet’] is treated in these types of anaerobic digester tanks.

“Then we have the ‘dry’ technology which is widely used in Europe where organic waste, such as food scraps, yard waste, poultry manure or other biomass is loaded into an enclosed, oxygen free chamber that has is then inoculated with the microbes necessary to perform the organic breakdown.”

Ruckert says that in the “dry” digesters you can monitor temperature, oxygen, moisture, and pH to control all the processes so it truly approaches a concept of zero waste. In other words biogas is produced, digestate is produced that can be composted, and some liquid would require treatment.

As example, Ruckert describes what happens with the organic waste from an industrial food processor. “All the peels, other food preparation scraps that cannot be delivered to a food bank, and unusable product is collected in a truck, transported, and then offloaded into the enclosed chamber. The liquids are removed and collected and the remaining solids are exposed to a heat source. As the solids and organic liquids are decomposed, the microbes generate methane gas, which can be collected and can be used in a combined heat and power [CHP] system whereby electricity can be generated.

“Then this CHP product could fuel the processing plant so it can minimize the reliance on outside energy dependence. And if heat is needed for an offsite drying or industrial process, then that heat from the biogas combustion can be diverted to that location.”

Ruckert says typically, private contractors pick up the organic waste and these collection trucks drive it to the organics processor. The waste is unloaded in an environmentally enclosed building and is conveyed to equipment that separates the organic from non-degradable items.

“You wouldn’t think of it but organic waste is not just steak bones and peels. Depending on the source, it has its fair share of plastic bags, silverware, and grit, which has to be separated out. With this separation equipment process, an organic slurry
is produced.”

At this point, the separated slurry—sometimes this is referred to as a “puree”—can go to a dedicated digester, or it can be pumped to a wastewater digesting operation to be mixed with domestic wastewater or, “it could go to a digester on a farm operation and be mixed with manure.”

The biogas produced “is an asset to any municipality” and Ruckert says collecting organic waste is another step in the recycling process to capture the potential of what we throw out.

“We have the technology to make everything repurposed and eventually, who knows, there may come a day when landfills are a thing of the past.”

Bigger Chicken, Drier Air
Sometimes the unintended consequences of one policy reap benefits totally unexpected. The eastern shore of Maryland, for example, is home to a huge poultry production of more 7.5 billion chickens. But this produces 1.2 million tons of manure that after decades of spreading as fertilizer has created a soil that literally “can’t take it anymore.”

One option to handling manure is AD. The process of treating manure before use as a fertilizer is generally considered ­positive, since the resulting digestate product has higher proportions of mineralized ­plant-available nutrients than the untreated poultry manure, and there is significant odor reduction.

But beyond compost/fertilizing are a host of new technologies to repurpose manures that offer multiple benefits to production, industry, and the environment.

Enter the Maryland Animal Waste Technology Fund (AWTF), authorized in 1998 as part of the Water Quality Improvement Act that was under the State Department of Budget and Economic Improvement. With new mandates for nutrient management for the Chesapeake Bay, the program later became part of the Maryland Department of Agriculture (MDA) administered through its Office of Resource Conservation (ORC).

Louise Lawrence, who heads up ORC, says the ATWF is now part of a suite of grant programs that assist farmers to manage nutrients and use best management practices—from manure management to cover crops and more.

She explains that the poultry manure is a huge organic waste output and has tremendous potential beyond spreading in fields, but that new technologies that are “economically sound and would benefit the environment are needed to repurpose this manure.”

One option to handling manure is AD. The process of treating manure before use as a fertilizer is generally considered positive, since the resulting digestate product has higher proportions of mineralized plant-available nutrients than the untreated poultry manure, and there is significant odor reduction.

But beyond compost/fertilizing are a host of new technologies to repurpose manures that offer multiple benefits to production, industry, and the environment. “Our objective is to make sure that technologies answer business and conservation needs by aligning the economies that make sense for different farmers with different farm situations. But the technologies have to be reasonable, so that farmers who invest can realistically pay them off. This means that the developers must not only be creative, but demonstrate their commitment to efficient operation and maintenance as well.”

In the UK and the European Union (EU), making sense of organic waste has been an ongoing process for much longer and in a more widespread business arena than in the US, says Declan O’Connor, co-founder and innovator of BHSL Energy Centre from Limerick, Ireland. He describes how his technology was successful in demonstrating to the MDA the many requisite parameters of commitment, efficiency, and economy, which won his company, and a local Maryland poultry producer, a million dollar grant to prove the process. O’Connor explains the evolution of his technology.

“More than a decade ago, our family poultry farm was threatened with closure due to the strict regulations on ground water pollution. My brother, Jack O’Connor went to work to solve the problem and developed a fluidized-bed technology that answers the manure disposal issue through a unique patented combustion process. This creates enough energy to not only heat the chicken houses but allows excess to be sold as electricity back to the power grid.”

Fluidized bed technology is not new and is commonly used in coal-fired power generation.

O’Connor adds that after perfecting the process and attending an organic waste conference where he met US poultry producers, he invited several Maryland state Senators to visit Ireland and learn first hand what this could do to address multiple production and environmental issues.

After their visit he recalls how the policymakers said, “We’ve seen the future, and we need this.” BHSL was then connected to the AWTF and to a local poultry farmer, Bob Murphy, whose farm was awarded a technology grant to test the process, with the additional commitment of another 3 million by BHSL.

Don’t Fight It, Burn It
Bob Murphy talks about the success and positive impact the BHSL Energy Centre is having on his 160,000-bird farm that now makes a new use for the more than 3,600 tons of litter created each year.

“I was looking down the road at what we were going to have to do. We can’t apply this to the land anymore; the soil is already oversaturated with phosphorous. When the MDA connected me with the BHSL people they said ‘We’ve got a plan. We’re going to generate electricity, heat the chicken houses, and burn this poultry litter efficiently, and you’ll have some leftover to sell on the grid.'”

“Prior to that we were trucking this to other
farms and industries who could use this, but I knew we couldn’t do this forever and we had to find new options,” says Murphy.

He says birds get graded on efficiency, a good feed conversion and good heat conversion and so far he is very pleased at the outcomes.

With this process, the fluidized bed technology takes the manure collected in a separate shed and delivers it by conveyer belts to the BHSL unit. It passes into a chamber with superheated sand where it burns and creates the energy used to either heat water for the poultry houses, or to be sold on the grid. And the small percentage of leftover ash is useful fertilizer additive.

“The system is similar to a radiator system,” says Murphy.

“There are heated pipes in each chicken house that have fans that blow on them to deliver dry heat. Immediately we noticed a ­difference in humidity and odor, which means no ammonia. And the benefit of a lowered ammonia from the litter in each house from the dry heat helps increase production so we have larger, more healthy birds for market.”

The BHSL has put an end to the farm using costly propane, creates a smaller carbon footprint, and has made Murphy an evangelist to the process with his local producers. “I tell them don’t fight this manure issue. We are only going to see more restrictive measures on how we dispose of this organic waste. I tell them you need to get on board with this, this is the ticket.”

Murphy adds he applauds how the system is also helping them to keep the Chesapeake Bay clean.

Not Every Wastestream Is the Same
Maximizing their customer’s energy potential of organic waste is all in a day’s work, says Aaron Zahn, CEO of Florida-based BCR Environmental Corporation and NuTerra Management, LLC.

“The company goals are to develop technologies that convert organic waste into environmentally responsible products. Our public -private partnerships in Florida alone have completed $180+ million in organic waste recycling facilities. Plus, BCR is the only company in the 30-year history of the US Environmental protection Agency [EPA] to develop and obtain national regulatory approval for new technologies that convert human waste to recycled usable materials. All other options are based on legacy technologies invented in the early 1900s or before.”

Contemplating how and where human waste, or what is known as “biosolids,” will be used might suggest a bit of “do you really want to really see how the sausage is made?” for the more squeamish, but Zahn emphasizes that their processes “totally transforms the waste to a product indecipherable from fertilizers purchased in home improvement stores.”

According to the Composting Council about 96% of food scraps are sent to landfills with only 4% being recovered for AD or recycling. While there are techniques to limit the amount of methane from the waste decomposition it is not the exact science that exists in an AD. The Council also reports that each person produces 60–80 pounds of biosolids each year which is treated by wastewater plants and half of this goes either to grow food or crops and the rest is incinerated or goes to landfills which adds greenhouse gases of carbon dioxide or nitrous oxide to our atmosphere. They cite nitrous oxide as being 298 times more warming to the atmosphere than carbon dioxide.

“Every town has a wastewater treatment plant and whether you are a small 5,000 person rural town or a city of multi-millions, we’ve perfected our processes to be economically viable solutions to harvesting and using these biosolids for beneficial purpose that is environmentally responsible,” says Zahn.

He explains that energy, how much you use, and how much you can harvest to make it a worthwhile investment is key to using biosolids. He says that their system uses 90% less energy to process biosolids than traditional wastewater systems.

“Wastewater plants consume 3 to 4% of all energy produced in the US, incredibly, they use 40% of the entire municipal budget, and are the single largest consuming group of energy.

“Our technology helps municipalities save a huge portion of their wastewater treatment budget by reducing their operating costs, energy consumption, and improving the local community environmentally with less noise, dust, and odor that are all inherent to the transportation of waste through neighborhoods.”

Zahn adds that at the end of the process “The municipality benefits financially from the output as the wastewater solids can be recycled into high value biosolids. For any municipality facing nutrient runoff issues, erosion, and emissions issues at landfills and other disposals, we have the perfect solution as we harvest the nitrogen, phosphorous, and potassium, and essentially create a high quality, valuable ‘new dirt’.”

Municipalities whose existing wastewater treatment plant systems cost them valuable cash, time, real estate, and resources need to think about a complete change of mindset. In a world where new technologies are available that are cheaper and better rather than trying to upgrade their existing systems with outdated legacy approaches, he suggests.

“We are offering a scalable solution that all runs right on your property. Here’s how it works. After the raw sewage is separated from the water, we pick up the solids into our facility and using a basic chemistry recipe in our facility convert the waste to usable sterile fertilizer. Because the process is recipe driven it works the same every time. Our facilities are a more cost-effective, energy-efficient, simple, odor-free, and environmentally-responsible approach than the traditional aerobic digesters, anaerobic digesters, and thermal dryers that have been used over the last century.”

“Our facilities disinfect, deodorize, and reduce the mass so when it comes out you couldn’t tell that product from a load of high quality topsoil. It looks and smells just like dirt.”

By improving the carbon footprint through 90% energy reductions and capturing the valuable nutrients to reuse, the process keeps those nutrients from “going down the drain” literally, and leaching into the soil. Municipalities can sell the biosolids to agriculture, to turf grass users like golf courses or sports fields. The recycled fertilizer can also supplement sandy soils as Zahn says “they are about 50% organic matter with a beneficial chemical content of 6% Nitrogen, 2% Phosphorous, and 1% Potassium.

There are few sustainable solutions to reusing wastewater biosolids, particularly at the smaller levels, Zahn says. NuTerra’s process is the same at a large or small facility, it is only a matter of building the modular processing unit to size, using the consistent technology, rather than trying to shoehorn one inflexible model size into diverse settings to “make it work.”

“This means we can deliver an economically viable and environmentally responsible solution anywhere in the world—a small town in the US or a provincial capital in India—it’s totally suitable in either place. And it’s like giving low cost, clean water to the market, and who doesn’t want that these days,” says Zahn.

Feeding the Tiger
Audiences watching nature videos of a tiger making short work of prey for dinner can hardly fail to be astonished at the big cat’s speed and efficiency of the job at hand. William Kish, director of business development at Ecoverse, maker of the Tiger depackager, says customers watching their unit at work are equally astounded.

“When we say there is nothing like it, truly there isn’t. This is really an all-in-one unit, manufactured in Italy where it is use in Europe. Ecoverse was awarded the North American (US and Canada) contract for distribution. The Tiger takes packaged—and also unpackaged—organic waste in literally any form, and renders each component both the food and packaging, as separate commodities ready for recycling, digesting, or another repurpose.”

Kish explains that with nearly 100 million tons of food that is discarded in the US, the headache to separate the organic from the packaging is overwhelming for the food waste brokers who collect everything from unsold packaged retail foods, grocery items, and restaurant organics. He explains how the food chain, literally the fate of discarded, packaged food items, works.

First, tractor-trailers collect the discards on a regular basis, “and the next step—separating the packaging like cardboard boxes that contain eggs in Styrofoam containers—is a huge challenge.”

“But with the Tiger, every bit of these are reusable. It’s just a matter of separating the paper, Styrofoam, and eggs into discrete collections.”

Using the eggs as an example Kish describes how the Tiger makes short and efficient work of anything you put into it, at the rate of up to 30 tons an hour.

After the delivery to the Tiger site, a front end loader with a 6-yard bucket picks up a the cardboard boxes containing the styrofoam packaged eggs and dumps it into an 8-cubic-yard hopper. This is the first step.

“The augers in the hopper go to work where one auger is feeding, the other auger is reversing—this prevents the food waste from bridging,” says Kish.

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