Where Does It Come From?

As you may know, hydrogen is the most abundant element in the Universe, and is very common on earth. Hydrogen is the simplest of atoms, composed of one proton and one electron. But pure, diatomic hydrogen (H₂)—the fuel of choice for fuel cells — does not like to exist naturally. Because hydrogen easily combines with other elements, we are most likely to find it chemically bound in water, biomass, or fossil fuels.

To get hydrogen into a useful form, we must extract it from one of these substances. This process requires energy. Accordingly, the cleanliness and renewablility of this energy is of critical importance. While a hydrogen fuel cell operates without producing emissions, making hydrogen can produce significant greenhouse gases and other harmful byproducts. Once obtained, though, hydrogen is a nearly ideal energy carrier. The various ways to get hydrogen are described below.

You may have observed this process in a high-school chemistry experiment. Water electrolysis involves passing an electric current through H₂O to separate it into hydrogen (H₂) and oxygen (O₂). Hydrogen gas rises from the negative cathode and oxygen gas collects at the positive anode.

Electrolysis produces extremely pure hydrogen, which is necessary for some types of fuel cells. But a significant amount of electricity is required to produce a usable amount of hydrogen from electrolysis. Ideally, this would come from renewable sources like wind and photovoltaics, and in the long term, it will. But hydrogen fuel promises little greenhouse gas mitigation if a developing hydrogen economy increases demand for fossil-fuel electricity.

Hydrogen can also be extracted or "reformed" from natural gas. A two-step process at temperatures reaching 1100°C in the presence of a catalyst makes four parts hydrogen from one part methane and two parts water (CH₄ + 2 H₂O >>> 4 H₂ + CO₂). It is a relatively efficient and inexpensive process, and can be made still more efficient with harvest of the waste heat (commonly referred to as cogeneration). This latter feature makes steam-methane particularly attractive for local use.

While this process is well understood and can be implemented on a wide scale today, it produces moderate emissions of carbon dioxide. This byproduct need not be pumped into the atmosphere, though, as it can also be profitably re-sequestered at the wellhead, providing a greater yield. Other innovative carbon-sequestration techniques are in development.

Unlike renewable electrolysis, steam-methane reformation depends fluctuating price of natural gas. Nonetheless, steam-methane reformation is poised to be the near-term hydrogen production method of choice on the road towards completely renewable methods.
(Source: www.hydrocarbonprocessing.com/archive/archive_99-12/99-12_insight.html)

Hydrogen can be extracted from hydrogen-rich biomass sources like wood chips and agricultural waste. When heated in a controlled atmosphere, biomass converts to synthesis gas, which primarily consists of carbon monoxide (CO), carbon dioxide (CO₂), and hydrogen (H₂).

Gasification technology has been under intensive development over the last 2 decades. Large-scale demonstration facilities have been tested and commercial units are in operation worldwide. Fortunately, biomass gassification's past hurdles have been economic rather than technical. Until recently, biomass gasification has been employed to produce low-value products like electricity or heat, which rarely justify the capital and operating costs. But the increasing demand for hydrogen promises to make biomass gasification economically viable in the near future.

Photoelectrolysis uses sunlight to split water into its components via a semi-conducting material sandwich. It is roughly like immersing a photovoltaic cell in water, whereby the incoming light stimulates the semiconductor to split H₂O directly into its constituent gases. Though promising, this is still an experimental method of hydrogen production that has not evolved beyond the laboratory.

Vast coal resources have often been viewed as a potential hedge against future energy needs. Unfortunately, coal mining pollutes and despoils the landscape, and burning coal produces many harmful emissions. Yet coal does contain hydrogen, and techniques are being developed to sequester the remaining carbon. The Department of Energy (DOE) sponsors many of these programs. These processes generally involve coal gasification to produce hydrogen and electricity, followed by reinjection of CO₂ or mineralization via carbonates.
(Source: www.lanl.gov/energy/ziock/ziock.html)

Certain species of green algae produce hydrogen in the presence of sunlight (biologists have known of these algae for some time). In the summer of 2001, researchers manipulated the photosynthetic process of spinach plants to produce hydrogen. But these biological means of hydrogen production, like the photoelectrolytic process described above, are known only as immature lab experiments. Intense research persists to better understand ways to improve these hydrogen production methods. Quantum leaps in this field could be the equivalent of striking oil.
(Source: http://www.ornl.gov/divisions/ctd/march2.htm)