- Created: Friday, 08 July 2011 12:36
- Published: Friday, 08 July 2011 12:36
By Mark S. Kuhar
In 1989, Dean and Belinda Soiland of BoDean Co. took over a quarry in Santa Rosa, Calif. – a site that had been in various states of operation for more than 100 years – and began producing material using a portable plant. It was a simple beginning. They probably never figured at the time that the quarry would one day feature the first aggregates plant in the world to be 100 percent reliant on solar power.
The Mark West Quarry photovoltaic system, which went live on May 9, will be capable of generating 1,165,000 kilowatt hours of green energy per year. The electricity produced by the solar panels will offset the release of 1,844,521 pounds of carbon dioxide annually, which is enough energy to power 190 typical American homes for a full year.
Going solar not only made business sense, it fit into the company’s mission.
“It is our desire to operate in an eco-efficient manner that is dedicated to sustainability,” General Manager Bill Williams said. “It does not make sense for us to continue to use fossil fuels to do this when we have the best energy source at our fingertips: the sun.”
If you discount the field of solar panels imbedded into the hillside adjacent to the quarry, on the surface, Mark West Quarry looks much like any other 750,000 tpy aggregates operation in California. Production begins at the quarry face, where the company blasts twice per week on average. They do their own drilling and blasting, using an Ingersoll-Rand drill and Alpha Explosives.
After a blast, Cat 988H loaders are used to move material from an upper bench to a second lower bench. Material is then moved via loader from the push pile to a Telsmith primary jaw crusher.
From the primary, material goes to a surge pile, where rock is routed to Remco and Telsmith secondary crushers for further reduction. The circuit also includes a wash plant, featuring a triple-deck screen and a spiral-paddle Greystone twin blade mill. In keeping with its mission to operate in an environmentally responsible manner, wash water is recycled using a 100,000-gal. closed-circuit holding tank. From the wash plant, water goes to a Phoenix Process Equipment clarifying tank. A Diemme plate and frame filter press is then used to convert the sludge and fines to 1-1/4-in x 1.5-meter-square cakes (see sidebar). Clarified water is returned to the 100,000-gal. holding tank for re-use.
Many quarry operations have implemented a process to create cakes from fines, but few have been able to find a marketable end-use for the product. According to Product Manager Charlie Young, Mark West Quarry has found several local sources that use the cakes for reclamation projects and pond lining.
Mark West Quarry makes a wide range of aggregates products, and uses much of the material it produces at its Santa Rosa asphalt plant, and at Northgate Ready Mix, operated by Troy Soiland, Dean’s brother.
The remainder of the material produced at the plant goes to local customers in the Sonoma and Napa county markets of California.
BoDean Co. owners, Belinda and Dean Soiland have made the BoDean Co. an industry leader in sustainability and eco-friendly mining operations. In addition to the use of solar, the company is also dedicated to the extensive use of recycled materials in its production process, as well as actively pursuing a managed reclamation plan that coincides with quarry operations.
According to Williams, there are six reasons the company chose to embrace solar power.
- It makes economic sense. Because of the federal grant program, the company is able to finance the system so that payments are equal to what they have been historically paying the utility.
- They recognized that they would see an immediate improvement with cash flow because of Pacific Gas and Electric (PG&E) rebates over the next five years.
- Tax depreciation associated with the equipment brings about a reduction in quarterly estimated taxes.
- Energy costs continue to rise. In seven years the system will have paid for itself at which time its energy will be free and clear.
- It is the right thing to do. It takes a tremendous amount of energy to crush, screen, wash and convey the rock product the company produces each day. Most of America’s electrical need is met by burning fossil fuels. By using the sun’s rays they are using a sustainable source that is clean.
- As a company they committed to sustainability and ecoefficiency.
Going to a solar-powered system took a lot of strategic planning and transition time. “We put the project out for bid in June 2010,” Williams said. “The actual construction began in late
November 2010. Therefore from start to finish the project has taken approximately 10 months with five months of construction time. However, the vision for this project was in the works years earlier. Our vision for this project began in 2006 when we installed solar panels at our main office in Santa Rosa. Like many things it started with a comment that seemed crazy at the time. If we had to do it all over again, we would not have waited. It does not seem crazy today.”
Even with the best idea and careful planning, the project had its challenges. From a philosophical standpoint, they had to demonstrate to everyone on the management team that such a system would pay for itself and make economic sense. “From a logistical standpoint regarding construction, the panels needed to be placed upon a steeply graded hillside,” Williams said. “To our knowledge, solar panels had never been placed upon a hillside as we were proposing. How were we going to place the piers for the racking system under such conditions? And how much was that going to cost?”
Through the bid process they discovered a company that developed a racking system that would fit their environment by using a screw mounting system. Problem solved.
In addition to its move to solar power, the company also conducts energy audits at its rock and asphalt plants to see where it can operate more efficiently and consume less energy. This is done by “using variable frequency drives where applicable, insulation of hot oil lines and utilizing recycled material in our production process both at our quarries and at our asphalt plant,” Williams said. “We are moving away from “Hot Mix Asphalt” (HMA), to “Warm Mix Asphalt” (WMA), paving and grading our properties so that our rock stockpiles face the south so that the heat from the sun is used to dry our product, and reclaiming mined land. We are also researching new technologies currently being developed that use the Sun to heat the hot oil needed for our asphalt production.”
It did not take long for BoDean Co.’s efforts to be rewarded. The company was honored at the Solar Leader’s Circle Awards Ceremony for Sustainable Business Practices on June 28 at Paradise Ridge Winery. The event was held by Pacific Gas & Electric (PG&E) and Solar Sonoma County to celebrate the energy efficiency, solar and
carbon offset of PG&E customers in the North Bay area of the state.
Mark West Quarry converts sludge and fines from its wash plant into a saleable filter cake product using a process from DIEMME Filtration, which designs and builds complete water recovery and slurry dewatering systems for sand and aggregate washing plants. These high-performance systems minimize water usage and minimize solid disposal problems.
The water recovery and sludge dewatering plants supplied by DIEMME Filtration are generally made up of the following stages:
1. The sludge well receives the slurry to be treated from the wash plant. It is equipped with a lifting pump.
2. The flocculant dosage station dilutes and adjusts automatically the dosage of the flocculant necessary to accelerate the process of solid-liquid separation.
3. The clarifier allows theseparation of the water (overflow) which can be used again, and the solids (underflow) which are discharged as a concentrated slurry.
4. The clear waters storage tank holds the recovered clean water before being returned to the washing plant.
5. The sludge storage tank receives the concentrated slurry from the underflow of the clarifier and serves as an accumulation and feed tank for the sludge dewatering stage. This stage is recommended to allow the filter press to be fed a consistent slurry at a rate independent of the clarifier underflow supply.
6. The sludge dewatering process is usually carried out with a plate filter press which has the following advantages: high dewatering performances; elimination of environmental and safety problems associated with tailings dams; high water quality and maximum recovery of washing water; and delivery of a very compact and dry filter cake product which can be used as a stable filling material in construction.