How do you combat a necessary evil on a budget? That's the dilemma with carbon capture. Scientists, policy makers and energy companies all agree that carbon dioxide from coal burning plants needs to be kept out of the atmosphere. The problem is how to do it without running up expenses that will make China, India, the United States and even Europe retreat behind years of prototype trials.

Thus far, carbon capture and sequestration (CCS) has been concerned with research and very little about actually putting the technology to real use. In Part I: Carbon Storage, the Money and the Market, we examined the history of carbon capture. In Part II: Carbon Economics, we dug into the forces driving the carbon market. Below we'll look at some of the new ideas in carbon capture.

Part III: New Ideas in Carbon Capture

Storage Through Careful Burning
Rather than store CO2 underground, some companies claim they can sequester carbon in the power plant where it is generated depending on how the coal is handled. The process complements underground storage.

A. Pre-Combustion Treatment
Even before coal gets burned, it can be treated so there is less to capture and store. The CO2 removed in this stage of the process needs to be stored, but it's easier, say advocates, to capture and store CO2 early in the process than when it comes out of a smokestack. 

Source: Vattenfall

One of the leading pre-treatment companies is CoalTek. The firm reduces the moisture content in coal to optimize plant efficiency and make the coal "cleaner" before combustion.

Novomer, a competitor to CoalTek, is a green chemistry company using carbon dioxide as an ingredient for a chemical process that produces uniform polymers, plastics and other chemicals. Its goal is to turn these materials into green environmentally friendly materials. Dow Chemical Company is another actor in this field. And there is also Microcoal, which process cleans up coal pre-combustion by basically microwaving it.

B. Old-Style Gasification
If you talk to Siemens or GE, they will tell you they've been doing CCS with integrated gasification combined cycle plants (IGCC). In a nutshell, the process turns coal into synthetic gas and removes impurities before combustion.

The gas is used to power a combined cycle gas turbine where the waste heat of the turbine is powering a steam turbine system.

C. New-Style Gasification
Great Point Energy says it has a technique for converting coal and biomass into pipeline-grade natural gas while also allowing capture and sequestration of the carbon dioxide.

"We can take coal out of the ground and put it in a natural-gas pipeline for less than the cost of new natural-gas drilling and exploration activities," said CEO Andrew Perlman, to MIT Technology Review.

The base of the technology is a recyclable catalyst that lowers the level of heat that is required for the gasification process and also transforms the coal into methane from its gasified state.

D. Underground Mining
Laurus Energy doesn't want to dig coal up. It wants to burn it underground. Borrowing technology originally developed in the former Soviet Union, the Houston-based company wants to popularize a technique for using coal as a form of energy that it says will be both comparatively environmentally friendly and economical. Scotland is conducting similar experiments.

An underground coal gasification project is more or less like coal mining without a mine. Instead of an open pit you dig wells in the ground reaching down to the coal resources. Then you inject oxygen and saline water turning the coal into gas.

The clean synthetic gas produced from the underground coal resources can be used for pretty much the same purposes as natural gas: power generation, gas for home heating, hydrogen, methanol and transportation fuels. It can also be used for pre-combustion carbon dioxide capture.

The method of underground coal gasification poses no risk to shallow fresh groundwater since the depths are below 1,000 meters, says the Alberta Energy Research Institute (AERI). And being underground it's more environmental friendly compared to traditional coal mining or coal gasification methods, but of course not near as clean as solar or wind power.

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