Green Methanol to Hydrogen--A Versatile Solution

There is broad agreement that green hydrogen should play a significant role in reducing greenhouse-gas (GHG) emissions globally. The question is, how will vast amounts of green hydrogen be made and distributed to the point of use? Previously, I posted a short paper introducing the concept of methanol as a green-hydrogen carrier.[1] In this paper, I will expand on why methanol is an excellent option to make green hydrogen efficiently and at low cost.

Conventional wisdom teaches that water electrolysis is the preferred path to green hydrogen. However, the U.S. electric grid is supplied by a mix of power generating means, and only about 17% of generated electricity is from renewable sources. This includes hydropower, which accounts for about 10% of generation. The remaining 7% is derived from wind, PV, biomass, and other less significant renewable sources.[2]

The carbon intensity of the U.S. electric grid (2018 data) is 0.453 kgCO2e/kWh.[3] Splitting water by passing electric current is energy intensive, consuming 50 to 55 kWh/kg hydrogen produced and resulting in a high carbon intensity of more than 22 kgCO2e/kg hydrogen.

Over the past 15 years, wind power and PV have captured an ever-increasing share of total U.S. power generation (see Figure 1). Also plotted in Figure 1 is the industrial electric rate because we assume that this is the rate most likely to apply to companies manufacturing hydrogen via electrolysis (rather than the residential rate or commercial rate, both of which are higher by about US$0.08 and US$0.04 per kWh, respectively). Notice that over the past decade, the average industrial rate for electricity has remained flat despite the addition of renewable generating capacity. Some have suggested that adding renewable generation to the national grid will drive down the cost of electricity—the data does not support this.

Figure 1. U.S. Net Electricity Generation vs. Average Industrial Price

Looking to the future, the average price of electricity in the U.S. is forecast to remain flat (see Figure 2). This has significant implications for the cost of hydrogen made via water electrolysis. If we use 50 kWh electricity per kg hydrogen, and an electric rate of US$0.07/kWh, the cost of electricity alone to make hydrogen is US$3.5/kg. This price is 31% higher than the national average price of diesel fuel (US$2.67/gal[4]) and it does not include any operating costs other than electricity. Also, this would not be green hydrogen as the GHG emissions attributed to grid power are substantial (22.65 kgCO2e/kg hydrogen). To approach zero GHG emission and green hydrogen, the grid needs to be 100% renewable. This is a formidable challenge and one that is unlikely to be achieved.1

Figure 2. U.S. Average Retail Electricity Price[5]

What is needed is a pathway to green hydrogen that is not reliant on large amounts of electric energy. That pathway is renewable methanol.

Annually, more than 95 billion liters of methanol are produced globally. It is the most shipped chemical commodity. Although most methanol is made from natural gas, there is a growing trend to manufacture methanol from low-carbon-intensity feedstocks including biomass, municipal solid waste (MSW), and even CO2 captured from industrial waste streams or from ambient air. An excellent overview on renewable methanol, including a list of commercial operations, is available from the Methanol Institute.[6]

When mixed with water, methanol is easily converted to hydrogen and CO2. The resulting net CO2 emissions are low to zero if the methanol is synthesized from renewable feedstock. However, a more detailed analysis shows that the carbon intensity can actually be negative in certain cases.

For example, the Enerkem plant in Edmonton, Alberta, converts 100,000 metric tons annually[7] of solid waste that would normally be destined for the landfill, producing renewable methanol instead. That solid waste, if buried in the landfill, would slowly decompose and release CO2 and methane[8] into the environment. By using the waste stream to make renewable methanol, the release of GHGs into the atmosphere is avoided. This “avoided emission” serves to drive the carbon intensity of the resulting renewable methanol to a negative value. A study published by Argonne National Labs indicates that the renewable methanol feedstocks with significant avoided emissions include landfill gas, anaerobic digester gas, and biomass.[9] The potential for renewable methanol as a feedstock to make green hydrogen is evident by the low (even negative) carbon intensities shown in Figure 3. To put this in perspective, methanol made from MSW has a carbon intensity of 2.15 kgCO2e/kg hydrogen or less than 10% the GHG emissions from water electrolysis.[10]

Figure 3. Well-to-Wheel Carbon Intensity for Renewable Methanol

Methanol is also an affordable feedstock resulting in low-cost hydrogen when the conversion is carried out at high energy-efficiency. For example, during the last half of 2020, methanol was trading between about US$250/MT and US$300/MT (Europe, U.S., and Asia), yielding hydrogen at a cost of US$1.91/kg to US$2.29/kg, respectively. Of course, reforming methanol with water yields carbon oxides in addition to hydrogen, necessitating purification before the hydrogen may be used by a fuel cell. However, compact and affordable processes are commercially available[11] to separate hydrogen from syngas and deliver high-purity product hydrogen meeting ISO 14687 (2019) purity standards for fuel cell applications (both stationary and transportation).

In summary, renewable methanol is an affordable pathway to green hydrogen, worthy of consideration especially for vehicle applications.

[1] The case for methanol as a green hydrogen carrier | LinkedIn

[2] Electricity generation, capacity, and sales in the United States - U.S. Energy Information Administration (EIA)

[3] 2020_09_emissions_factors_sources_for_2020_electricity_v14.pdf (carbonfootprint.com)

[4] https://www.eia.gov/petroleum/gasdiesel/

[5] The price shown is the average of residential, commercial, and industrial electricity rates. The industrial rate is less by about US$0.03/kWh. In other words, the industrial rate for electricity is forecast to remain flat at about US$0.07 through the next 30 years.

[6] https://www.methanol.org/wp-content/uploads/2019/01/MethanolReport.pdf

[7] https://enerkem.com/company/facilities-projects/

[8] Methane is 84-times more potent than CO2 as a GHG, https://www.edf.org/climate/methane-other-important-greenhouse-gas

[9] https://ngi.stanford.edu/sites/g/files/sbiybj14406/f/Methanol_LCA_presentation_as_Stanford%20Workshop-201707.pdf

[10] In comparison, burning one gallon of diesel results in the emission of 10.2 kg CO2

[11] https://www.e1na.com/