Most of the time, I try to give tips on how to make your plant energy efficient. However, with expected new government regulations, we now have to be concerned about carbon efficiency. As state and federal regulators start discussing carbon credits, it’s an absolute certainty it will cost your plant more money. No matter how you try to avoid it, you’ll probably have to pay for energy production with a carbon-related tax.
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However, by incorporating biomass into the equation, you may be able to reduce your carbon footprint. The argument for biomass is simple. Trees capture carbon, so if you cut down a tree and burn it, it’s OK as long as you plant another. Some states already have passed laws making biomass energy a “carbon neutral” source.
So, how will that help your plant? The most efficient use of biomass is for heating, not power. Replacing current natural-gas or fuel-oil steam boilers with wood burning boilers reduces net carbon footprint without actually reducing energy use. Switching to more steam-heated equipment and away from direct fire can drastically reduce entire plant net greenhouse gas production.
Biomass also can be used in process heaters, but the nature of the firing may create too much swing and would make it difficult for a quick shutdown. Steam production is safer because excess steam can be vented and leaks wouldn’t fuel the flame.
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Although talking about wood-burning stoves seems like a step backwards, today’s systems have been made efficient. In addition, there can be various sources of natural feed for your unit and you can design the system with a natural-gas, or fuel-oil backup system in case of supply or equipment problems.
This is necessary for those already in the wood processing industry. Carbon credits generated from either using unwanted byproducts or selling that waste to a close-by industrial plant may lead to an industry all by itself. Now trees can be harvested to produce carbon credits and in areas where annual forest fires can be a problem, creating wide firebreaks can be profitable.
Economics of a biomass boiler depends on a few key factors. First, you must have a renewable source within good proximity to the plant and a method of transporting the energy supply. Trees needn’t be the only source. Corn husks, straw, and organic waste (from a renewable source) can all be used. Trees are usually processed into wood chips while other biomasses are made into pellets. The raw material can be dried with low level heating sources to increase overall efficiency. It’s essential to minimize transportation energy because it may be counted against the carbon credit. A plan must exist to replant what was removed, or else the carbon dioxide created isn’t being removed.
The boiler itself is a straightforward design. Biomass boilers are easy to maintain and operate. The latest designs have integrated advanced control systems that keep the boiler at optimum efficiency. Biomass is automatically fed into the boiler when demanded.
If you have a very old or inefficient oil or gas boiler or one that needs replacement, you also can gain an overall energy and NOx savings. Biomass boilers with integrated scrubbers can be highly efficient. Also, the net benefit to the community, because it will add jobs and use local products, will be great for the company’s image.
The downside is that these systems have greater capital costs. However, current energy-related credits might make them cheaper. You also will need a place to store biomass and have the equipment to create the chips and pellets. A joint venture or deal with an energy-related company could be possible. I‘ve heard that certain companies that supply steam or steam-related equipment may be looking at this as a natural extension of their business. The third party would require a long-term deal for steam, but this would relieve your plant of having to operate a new system.
For those who don’t need as much steam, these plants also come in a Cogen variety where high pressure steam produces electric power through topping turbines.
Gary Faagau is Chemical Processing's Energy Columnist. You can e-mail him at [email protected].
