06.10.11Frank Sinton, CEO, PMC BioTec

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"Water is the new oil," according to T. Boone Pickens. Indeed, the waste treatment industry is at the precipice of fundamental change, driven by the kinds of innovations that now propel electronics and medicine. One such pivotal change is that waste biosolids now represent an economical and ongoing source of energy, in the form of biogas, as well as valuable fertilizer components and clean water.

Millions of megawatts of renewable energy per year are waiting to be harvested by waste treatment operations in the U.S. and Europe. But until plant operators adopt the latest forms of biological treatment technologies to convert this enormous reservoir of biosolids, or sludge, into natural gas, this attainable source of renewable energy will continue to be squandered.

To appreciate the challenges of changing waste treatment practices to exploit that opportunity, it helps to understand why sludge is such an important problem.

Sludge is Expensive, Hazardous and Wasteful

Despite increasingly sophisticated environmental intervention strategies taking hold across a wide range of industries, the nearly 39,000 waste treatment facilities in the U.S. today use the same basic biological treatment processes developed nearly a century ago. While many such processes have been developed, such as fixed-film, suspended growth, trickling filter variant and activated sludge modification, they all hold one thing in common: they annually result in over 19 million tons of sludge needing stabilization and disposal at a burdened cost of up to $300 per ton.

In fact, the Environmental Protection Agency (EPA) estimates that the cost for sludge handling and disposal account for 40 to 60 percent of the total budget for a waste treatment facility [http://www.epa.gov/nrmrl/lrpcd/esm/projects/117990.htm]. Costs stem from the need to thicken sludge before disposal and stabilize it per Federal 503 Regulations for volatile solidsand vector attraction reduction, pathogen destruction, reduction of toxic heavy metals content, and control over nitrogen and phosphorus loading rates to prevent over-fertilization.

Biosolids are problematic beyond just volume and disposal cost -- they contain sewage contaminants not broken down in the treatment process or carried away by the water effluent leaving the treatment plant. The most commonly detected trace contaminants of concern are heavy metals (arsenic, cadmium, copper, etc., some of which are also critical plant micronutrients), and toxic chemicals (e.g., plasticizers, PDBEs, and others, including personal care products and pharmaceuticals).

All of these factors make sludge a high-value target for biotechnological solutions. The widespread impact of these innovations will be clear after briefly reviewing the nature and limitations of current approaches to sludge handling, stabilization and disposal.

Existing Sludge Treatment Approaches Are Inadequate

There are a number of conventional sludge treatment/stabilization approaches. Both biological and physical/chemical processes exist that will provide pathogen reduction and sludge stabilization. However, they do not achieve much reduction in sludge mass, and the physical/chemical processes (e.g., lime treatment) generally increase the mass of sludge to be disposed significantly; this is a serious drawback since a key measure of waste treatment is the conversion rate of biosolids to clean water, biogas, recoverable minerals and nutrients.

The conventional alternatives for stabilizing sludge can be summarized as follows:

• Aerobic sludge digestion: Common at small treatment plants (less than 20,000 cubic meters per day, that is, 5 million gallons per day), aerobic digestion is simple, stable and predictable. In this process, the sludge is aerated for many weeks. Some of the sludge (less than 30%) is converted to mainly carbon dioxide and water. Thermophilic variations achieve rapid results in smaller volume. Negatives include the energy required for aeration, the small amount of waste sludge destroyed and the high cost of contaminated sludge dewatering and disposal.

• Anaerobic sludge digestion: Anaerobic sludge treatment is essentially a large septic tank with mixing and electrical instrumentation for monitoring, controls and troubleshooting. This is the most common sludge treatment for large plants, with low operating costs since aeration is not required. However, often less than 50% is converted to methane, carbon dioxide and water.

• Anaerobic CAMBI process: The CAMBI system utilizes high-temperature hydrolysis of sludge solids to improve anaerobic digester results and achieve complete pathogen destruction. CAMBI has enjoyed some success in the past decade. This process operates at lower pressure (12 bars, or 176 psi) and temperature (160°C) and utilizes the released organics to anaerobically generate more methane for heat recovery and reduce sludge disposal. A net increase in sludge destruction is reported to boost volatile solids conversion rates from 30-50% to 60%. CAMBI suffers from high capital and operating costs, odorous off-gas handling requirements, complex operation, and liabilities associated with pressurized and heated vessels.

  Legacy aerobic and anaerobic processes produce treated sludge (40 to 60% of the feed amount on average) that must be disposed of in some fashion. Sludge disposal is conventionally handled via costly and environmentally damaging options, summarized as Burn It, Dump It or Bury It, as follows:

• Incineration processes: Hauling sludge to an incinerator is convenient, though it does require a collection, dewatering and truck filling system. Costs vary widely depending on location and incinerator availability. In addition, incinerators have become increasingly regulated and the costs for permitting and building a new waste incinerator are becoming prohibitive.

• Landfills: Burying sludge looks inexpensive when only the tipping fees are considered. Rather, it is quite expensive when all costs for sludge preparation are accounted for -- most landfills require a minimum dryness, so liquid waste streams require significant pretreatment prior to disposal.

• Land application: Dumping waste sludge on farmland is common. Federal 503 regulations require varying degrees of sludge treatment and stabilization beforehand, depending on the land's intended use. Land application safety is controversial due to the many undesirable compounds (viruses, heavy metals, pathogens, endocrine disruptors, etc.) present in sludge.

• Anaerobic digestion with sludge drying and pelletization: There are several commercial variations on this theme, mainly in Europe. It offers the advantages of reliable high temperature destruction of pathogens with some degree of energy recovery and production of dried sludge fertilizer pellets. Disadvantages include a huge capital cost, an unreliable and seasonal market for the pellets, high energy requirements to dry the sludge, and a sludge drying off-gas issue.

• Ultra-screening: This loophole technology for waste sludge reduction consists of ultra-screening and hauling tons of sludge to a landfill as "screenings". This fails to meet the intent of the Federal 503 regulations and will not meet the proposed regulations to ban such organics-rich material from the rapidly shrinking landfill space.

Simply put, sludge is an extraordinarily resource-intensive and problematic byproduct of every waste treatment and disposal process to date.

A Better Way -- Efficient Microbiological Conversion of Sludge to Energy

As described above, the existing approaches to dealing with millions of tons of sludge are outdated, expensive and environmentally damaging. By contrast, the new advanced biotechnological approach described here is more efficient and cost-effective, obviating the need for most post-treatment sludge disposal and enabling nutrient recapture while generating more energy. It features the following characteristics:

• Particle size reduction and molecular manipulation: State-of-the-art, custom industrial particle size grinding equipment is combined with biokinetic measurements and respirometric testing to break down complex molecules and long chain polymers into very small (even nano-level) particle sizes and much lower molecular weights, increasing the "digestibility" of the biomass. The microbes (methanogens) in the anaerobic reactors are now able to convert these previously indigestible molecules into biogas in much less time.

• Nutrient recapture: Ultrafiltration combined with a nitrogen and phosphorus removal process eliminates these nutrients from sludge and makes them available for repurposing as valuable fertilizer.

• Biosolids elimination: With the high conversion rate to biogas and recovery of nitrogen and phosphorus, there is no need for energy-intensive, expensive treatment and disposal of residual sludge.

• Biogas (methane) generation: The acceleration of the biological treatment enables extremely high conversion rates of sludge solids to biogas -- up to 90% or more, compared to just 45% in conventional processes. Thus, much more biogas is generated.

These anaerobic treatment innovations are being retrofitted at facilities around the world, and designed into new anaerobic facilities. New plants include traditional municipal and industrial treatment plants as well as cellulosic ethanol, palm oil processing, algae biofuels and other biorefineries where residual biomass can now be converted to renewable natural gas (methane) as a valuable energy co-product.

The Future of Waste Treatment is Here

Environmental biotechnology, as shown in this article, is revolutionizing waste treatment. With the continuing emergence of biotechnology-based infrastructures that can essentially eliminate biosolids, waste plant operating costs can be reduced by millions of dollars annually, depending on a given plant's volume. Biosolids-to-renewable natural gas conversion can yield equally compelling cost savings.

Now that the technology exists, the next challenge will be for the waste treatment industry to embrace the entrepreneurs offering this and many other game-changing products and services.

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Reader's Comments

Date	Comment
Harry Valentine 6.13.11	Interesting article . . . raises many good points. Several cities around the world will have to consider using seawater to flush the toilets. While the presence of salt may slow the fermentation process, many fermented products are made with salt as part of the material to be fermented (by anaerobic digestion). Being able to extract combustible sludge from seawater would be a definate plus . . . the sludge could then become fuel for thermal power stations. This is an important topic that will need to be explored further . . . additional research and development definately needed in this crucially important area. Frank Sinton may just have opened the door to such further development.
Malcolm Rawlingson 6.15.11	Very interesting article Frank. Another option which I believe is being proposed in the City of Vancouver British Colombia in Canada is to clean the methane and compress it into the natural gas distribution system. If all sewage treatment plants did this then at least a portion of our gas supply could come from renewable resources and not be discharged into the atmosphere as it is now. The same principles could also be extended to the disposal of the billions of tons of animal manure that is produced annually. Combine the processing of animal wastes with the processing of human wastes and a sizeable amount of methane could be produced and injected into our natural gas distribution system for heating and other needs. These initiatives using current technology could meet a sizeable percentage of our energy requirements and allow our gas supplies to last much longer. Malcolm
Alan Muller 7.1.11	This article does not make sense to me. First, "Conversion of Sludge to Energy" is fundamentally impossible, except perhaps by nuclear reactions. Only chemical transformation is possible; all the original mass will still be there. Any time one sees this sort of claim, bullshit is being ladled out.... "State-of-the-art, custom industrial particle size grinding equipment is combined with biokinetic measurements and respirometric testing to break down complex molecules..." Doesn't make sense either. What is "biokinetic measurements and respirometric testing..." it is quite true that improvements in sludge management are needed (!) Real ones..... Alan Muller
Blake Wyndlow 8.17.11	Perhaps Alan Muller would like to look up: http://www.wrighttech.ca/Biodryer.htm This system will convert ALL organic waste into fuel without any external power source, without any odor or escaping gas to deal with and is completely silent in operation. I would suggest that you check with Disney World in Florida - in fact, if you are in a position of influence, I could arrange a visit, but as there a steady stream of visitors already visiting the site, it is becoming as popular as Disney World itself - well, almost. So, please open up your mind that not only is it possible to generate fuel from sludge, it is possible to do it well - all organic material is already being done well on a daily basis. No pollution, no odor and self contained Contact me at blake.wyndlow@gmail for additional information

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