06 June 2011 00:00 [Source: ICB]
Inside Agilyx's PTF plant
Dow announced on May 23 that it was able to recover 96% of available energy - equivalent to 11.1MMBtu of natural gas - after incinerating 578lb (262kg) of linear low density polyethylene (LLDPE) scraps generated in one of Dow's extrusion laboratories sited in Midland, Texas. The fuel produced was used for Dow's incinerator during the test.
The energy recovery trial was completed in compliance with regulatory permits, said Jeff Wooster, plastics sustainability leader for Dow's North American plastics business.
"Dow began making plans for this trial in 2010 and the project began after value chain partners expressed interest in how energy recovery for plastics could help them capture the embedded energy value in their products," said Wooster.
"The results of the trial provide a better understanding and first-hand knowledge of how plastics can be used for energy recovery," he added.
The company does not expect this type of technology to replace traditional means of recycling plastics. "Energy recovery and chemical transformation extend and complement traditional plastic recycling," said Wooster. "The US lags behind many other countries that capture trapped energy from recovered materials. Our next step is to help find a way to scale up this more sustainable practice in the US."
Wooster noted two types of company that could benefit from PTF technology: large energy users such as cement kilns; and firms that deal with nonrecyclable plastics. "The ideal situation would be when both companies collaborate," said Wooster.
Dow said it is working independently for this particular trial using only Dow scrap materials.
"All types of polyethylene (PE) and polypropylene (PP) are well suited to energy recovery because of their high embedded energy value," Wooster added. "For this energy recovery trial, the plastic film was loaded into containers and fed directly into the kiln without further processing."
Dow Chemical plans to conduct additional trials to study more opportunities for this technology, said Wooster. A report published in April on PTF developments in North America, conducted by US consulting firm 4R Sustainability and funded by industry trade group the American Chemistry Council (ACC), identified 25 companies currently dealing with PTF technologies. These were mostly using pyrolysis, where plastic waste goes through thermal treatment and sometimes pressure before being converted into a fuel product.
Other waste conversion technologies include incineration (as used by Dow), gasification, hydrolysis, anaerobic digestion and other chemical feedstock recovery. The majority of the PTF companies have pilot-scale facilities, the report noted.
"Development of pilot-scale facilities has generally taken most firms three to five years," 4R Sustainability reported.
"The financial resources that have been made available to developing the technology will also have an impact on the size of the facility."
The average recommended commercial-scale PTF facility capacity is between 7,000 and 10,000 tonnes/year, with the average costs of systems in a range of $4m-5m (€2.8m-3.5m).
US-based plastics convertion firm Agilyx is already operating a 3,500 tonne/year PTF facility in Oregon. The company said it can process all types of resins and can produce on average 1 gal (3.8 liters) of crude oil - primarily ultra-sweet synthetic crude - for every 10lb of mixed plastic.
The oil can be subsequently refined onsite via standard microrefinery technology or at existing refineries, Agilyx said.
New York-based converter JBI Global announced in early May that its first sale of 214 barrels of waste plastic-based low-sulfur heating oil went to US-based oil and gas firm Occidental Petroleum for $109.80/bbl.
JBI Global's Plastic2Oil (P2O) processing facility in Niagara Falls, New York, which started in December 2010, has a capacity of 7,000 tonnes/year and can convert mixed waste plastic into diesel, heating oil and light naphtha fuels. The company noted that it can produced around 1 liter of fuel for every kilogram of plastic.
"One of the key elements of our P2O business strategy is entering into agreements with industrial partners that generate significant amounts of waste plastics [or] consume significant amounts of fuel," the company said in its latest quarterly report.
The majority of the pyrolytic systems noted in 4R Sustainability's report can accommodate consumer packaging of all types, including categories 1-7, although some companies noted that polyethylene terephthalate (PET) and polyvinyl chloride (PVC) are not optimal for feedstock.
"PET and PVC are also less desirable because their fuel yield is considerably lower than other resins," the report noted. "The fuel yield for PET is just 30%, compared to polystyrene [PS] at 90% and low density polyethylene (LDPE) at 70%.
The yield for PVC is similar to PET but PVC also breaks down into hydrochloric acid during the conversion process."
According to the report, return on investment (ROI) is generally quoted at two to five years if all cost conditions and product pricing hold steady. Factors that could impact the length of ROI include changes in energy costs, price of oil and fuel, and cost and availability of scrap plastic. "Economic returns are seen in either the sale of the fuel product or the offset fuel costs if a company uses the fuel internally. A number of manufacturers said PTF-derived fuel is competitive to traditionally-derived fuel even if the price of crude oil drops to about $40/bbl," the report said. The report noted that it takes about 7.57lb of plastic to make 1 gal of fuel. In terms of energy value, the average Btu value of 7.57lb of plastic when incinerated would be about 117,424Btu. "Compare that to the 138,095Btu value of diesel, which also requires 7.57lb of plastic, and these calculations suggest that PTF yields better energy value from scrap plastics."
Despite the enormous potential of PTF technologies, the US still lags behind Europe and Asia in using these technologies. One reason is that many countries recognize plastic conversion as a form of recovery in their laws and regulations, said Steve Russell, vice president of the plastics division of the ACC. Another factor is the cheaper cost of putting waste in landfill in the US compared with other countries.
"The US currently recovers energy from about 14% of waste through waste-to-energy facilities. Japan and Europe use WTE to recover energy from 75% and 40% of municipal solid waste, respectively," said Russell. "There are many innovative energy-recovery technologies in use and under development today. The opportunities for tapping into the embodied energy of nonrecycled plastics are tremendous. Industrial scrap and municipal solid waste are cost-effective, abundant sources of energy for businesses."
SPUR TO INVESTMENT
The report recommended that creating demand for PTF products similar to the demand created for renewable fuels would be a likely catalyst for investment in commercialization of PTF technologies.
"Many of the PTF players in North America are hopeful that they will be able to secure investment for a commercial-scale facility in the next two to three years, if not sooner.
"The outlook for commercialization of PTF technology in the near term looks strong," the report concluded.
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