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Space Exploration and Colonization Demands Renewable Energy and Other Resources

image credit: Couresty,

Space exploration is rapidly catapulting into a new era of commercialization that is largely driven by the private sector. A perfect storm which is extremely bullish for business expansion in numerous sectors is brewing in the "Space space."

Morgan Stanley  suggests that this global industry's revenues will climb from today's level of $350 billion annually to over $1.1 trillion by 2040.

According to University of Pennsylvania's Wharton School, technology innovation is working its magic on driving down costs. Initiatives that further the practice and use of reusable rockets and boosters have a significant impact on cost reductions. Also, intrepid visionary Elon Musk recently noted that he believes SpaceX's reusable 100-passenger Starship will only cost $2 million per flight to operate in space. Musk additionally stated that "the costs include $900,000 in propellant to get into the Earth's orbit and an additional $1.1 million in operational costs." SpaceX's analytical insight tells us that rocket fuel is almost 50% of the operational cost that is just needed to "get the show on the road." Perhaps even more critically, propellant is acutely vital to get explorers home from the likes of Mars. Making fuel for return journeys from the Red Planet is a prime focus of mission planning.

Like any new, rapidly-growing enterprise, the burgeoning nouveau space-faring industry will only continue proliferating by effectuating efficient management of assets. Next to desert island situations and the like, off-planet ventures and associated extraterrestrial colonization endeavors present the most dire and challenging of resource scenarios. Previous blueprints for space faring largely entail "bring it with you when you come" strategies. For prolonged extraterrestrial travel and colonization efforts that will involve hundreds, if not thousands, of people, this approach is both impractical and unsustainable.

Rocket Fuel Is a Key Strategic Resource for Space Exploration

Paraphrasing George Orwell, "All resources are equal, but some resources are more equal than others."

Rocket fuel is in the category of energy and is arguably "more equal than others" when it comes to resources for planetary exploration. Over the last 60 years, the rocket development cadre of space exploration has utilized a wide variety of substances for fuels. This list includes a plethora of petroleum fuels and cryogenic ones such as liquid hydrogen. A list of 18 different propellants attests to the diverse variety of candidates that have been utilized at one time or another. While having choices is often desirable, it can also lead to inefficiencies for equipment production, manufacturing practices, and operational standardization resulting in chaos for supply chains and their resilience. A variety of considerations has led the industry to narrow down its fuel preferences to one common compound. Methane. Methane is the primary constituent in the fossil fuel, natural gas.

 Methane is also made biochemically and called "renewable natural gas", or RNG, as it is made from renewable resources such as biomass.

RNG & Other Vital Resources Can Be Made Simultaneously

The deft integration of proven technology platforms is generally a more reliable path for achieving technological goals instead of obsessively trying to "reinvent the wheel" to meet novel, target functionalities. This axiom was brilliantly illustrated in Arthur C. Clarke's short story, "Superiority." In this yarn, two adversaries use different approaches for deploying weapons systems during an interplanetary war. One antagonist is captivated with the allure of new, cutting edge technologies for armaments. The other combatant is content with a more parsimonious approach using "inferior" or passé science as a means to prosecute the war. Ultimately, unforeseen developmental challenges hinder the "new technology" provocateur while the planet employing technically-proven methods prevails. The winner was able to significantly amass conventional armaments which enabled them to soundly overwhelm their opponent.

Although commercial space travel and colonization efforts are not a war, there are elements of the example in the "Superiority" story that merit consideration. Additionally, attention to sustainability principles is paramount, particularly in resource-constricted scenarios.

Commercial space travel and colonization need to embrace a sustainability perspective as many resources are interlinked.

Interlinked resources are ones that are interrelated in one way or another and the concept was notably articulated by McKinsey & Company. These linkages can be either negative or positive. For example, in California, water is needed for farming, domestic consumption, and energy production. It takes energy to make water while water is also needed to make energy. It takes one to make the other and vice-versa.

Interestingly, food and fuel production are interlinked for space colonization and exploration enterprises.

These interlinkages can also be negative or positive. The challenge is to know which is which for a particular situation or circumstance and have the ability to leverage, and not be impeded by, resource interlinkages.

The Role of Biomass for Colonization Efforts

Biomass warrants serious consideration as a feedstock for the production of renewable resources since it is capable of producing multiple renewable products. It is important to appreciate that large scale vertical hydroponics operations are capable of producing of several tons of biomass per day. When hydroponics technology is coupled with advanced bioconversion technology, it is possible to generate methane and green ammonia and phosphorus, and water. These are all crucial resources that are required by human communities.

The biomass generated by hydroponics operation located on colonization targets like the Moon or Mars can be harvested and consumed by colonists or processed by the bioconversion system to make renewable energy, fertilizer, and water. Power for these systems is supplied with a solar power/battery system. A bioconversion system with an appropriately sized hydroponics plant can produce enough methane in 70 days to completely fill the Space X Starship methane tank. Additionally, the adjoining hydroponics plant will produce approximately 1 ton of oxygen per ton of biomass (based on photosynthesis chemistry) which can be used for propellant or breathed by colonists. Water and fertilizers are recycled using the bioconversion system to maintain the functionality of the hydroponics system.

A Lot Like Earth, But Much More Resource Efficient

The reality is that colonization habitats that are created on alien worlds will be Earth-like but probably similar to those on Class K planets envisioned on "Star Trek." Because of the environmental characteristics of the target planets, settlements will likely require use of massive domes to house human communities. Sustainability principles which are crucial on terra firma are exigently priceless in these situations because resource frugality is mission critical. Consequently, the challenges of extraterrestrial travel and colonization demand a greater focus on sustainability.

The colonization of celestial bodies in our solar system is an unprecedented step for life from planet Earth. In the vast history of migrations on our home world, planetary colonization efforts are perhaps analogous to those events that transpired eons ago when multi-celled ocean-dwelling creatures first occupied land masses on Earth. However, when organisms on our planet emerged from their watery abodes to conquer the land, resource sufficiency was not problematic. In order to prosper on foreign bodies in the solar system, terran lifeforms must manifest the highest capabilities of sentient functionality to realize the keenest level of resource management and sustainability. This thinking is crucial because Mankind's proposed new domains are virtually devoid of the basic materials needed to sustain life and civilizations as we know them.


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Bob Meinetz's picture
Bob Meinetz on Jan 7, 2021

"Methane is also made biochemically and called "renewable natural gas", or RNG, as it is made from renewable resources such as biomass."

Alan, total U.S. RNG production amounts to ~19 mcf annually.

Considering U.S. shale gas production is 22,320,000 mcf annually, it's unrealistic to think RNG will ever significantly offset carbon emissions from shale gas.

There is nothing renewable about methane, aka "natural gas", and never has been.

Roger Arnold's picture
Roger Arnold on Jan 8, 2021

There is nothing renewable about methane, aka "natural gas", and never has been.

Careful, Bob. "Never say never". Yes, the. amount of "renewable methane" produced for commercial use (that's excluding the amount of biologically produced methane from swamps, termites, and ruminants that goes straight into the atmosphere) is pretty trivial compared to fossil methane. But that could change.

One of the more plausible options for CO2 removal from the atmosphere involves growing and harvesting gigatons of algae annually from the oceans. The harvested biomass could be used to produce food, bio-plastics, hydrogen and synthetic fuels. Nitrates, phosphates, and other plant nutrients would be recycled to the ocean to continue the cycle. Depending on the processing employed, waste streams of either pure carbon or pure CO2 would result. Either could be sequestered to support CDR. 

The amount of "renewable methane" produced in that manner would probably still be small compared to current production of fossil methane, but it's on the same general scale. It could be adequate to support a post-fossil need for methane, without resort to production of synthetic methane from CO2 and electrolytic hydrogen.

Bob Meinetz's picture
Bob Meinetz on Jan 8, 2021

OK, two questions:

1) Including construction of another multi-$trillion infrastructure for harvesting methane from algae, when might it be economically advantageous to switch from the existing infrastructure for extracting fossil methane?

2) Removing CO2 from the atmosphere and converting it to methane increases its global warming impact by 80 times, or more. Could not leakage of CH4, combined with the energy costs of processing on such a massive scale, increase the overall climate impact of carbon captured from the atmosphere?

Alan Rozich's picture
Alan Rozich on Jan 8, 2021

1. Why are you mentioning algae? There are some 10,000 anaerobic digesters in the US that can be re-configured to double methane production from biomass. The CO2 produced by combustion/oxidation of RNG goes back into the atmosphere and is then converted by plants into biomass where one of the "waste" products of photosynthesis is oxygen.

2. Who said anything about removing CO2 from atmosphere and converting into methane? Are you referring to the method that involves the reaction of hydrogen and carbon dioxide using a ruthenium-based catalyst at temperatures of 300 to 400 degrees Celsius?  This is the technique that SpaceX "hopes" to use for return trips from Mars. It is not yet commercial by any means. Biological systems that process biomass do not require rare-earth metal catalysts since they employ enzymes for catalysis.

Bob Meinetz's picture
Bob Meinetz on Jan 9, 2021

"Why are you mentioning algae?"

You'd have to read the post to which I was responding.

"Who said anything about removing CO2 from atmosphere and converting into methane?"

Biomass removes CO2 from the atmosphere, anaerobic digesters convert it to methane. Over 100 years, methane has 80x the global warming impact of CO2 - so if even 2% of the produced methane leaks to the atmosphere, you've more than doubled the GHG impact of simply burning biomass for power.

In practice, an estimated 2.7% of extracted methane ("natural gas") is leaked to the atmosphere.

It's why livestock, though part of the terrestrial biosphere throughout their existence, are not "carbon-neutral" in any sense of the term. They're methane machines, converting photosynthesized sugars to a GHG that will last twenty times as long as they will.

Roger Arnold's picture
Roger Arnold on Jan 11, 2021

Fair questions Bob. Regarding infrastructure for methane production from ocean biomass, it probably would indeed grow to the multi-$trillion scale if a consensus developed that that was the way to reduce atmospheric CO2 levels and replace current natural gas production. But even if that happened, it would start out vastly smaller and then grow. Two decades of 50% annual growth is 14 doublings -- a 16,000-fold increase from the first year starting point.

I don't personally advocate that, and I don't think it's particularly likely. But we're talking about technical feasibility here -- at least I am -- not what's "best" or most likely.

Regarding methane's GHG contribution to global warming, the situation is complex. It's both better and worse than the figure of "80x more potent than CO2" suggest. The 80x, I believe, is for estimated effect averaged over a 200-year window. The "immediate potency" is much higher. Some 200x, IIRC. But the residence time for methane in the atmosphere is relatively short. It gets oxidized by hydroxyl radicals to CO2 and water vapor. I think it's twelve years that's typically cited as a kind of "half life" for residence of methane in the atmosphere.

I could be confusing that 12-year figure with the half-life of tritium, but I know it's close to that. So long as that average residence time holds, the contribution to GHG warming from methane leakage will be negligible.

The trouble is, atmospheric residence time is not an intrinsic property of methane; the rate at which it gets oxidized in the atmosphere can and does vary widely, depending on local conditions. I won't go into that, but if one is inclined to fret about doomsday scenarios, there are some real "doozies" involving methane spikes. The spikes could essentially overwhelm the methane oxidation mechanism, and the residence time scale would shoot from decadal to millennial. Or longer. We'd be toast.

Some of those scenarios, AFAIK, are scientifically plausible; I don't think we know enough yet to rule them out. Happy New Year.

Nathan Wilson's picture
Nathan Wilson on Jan 9, 2021

Well, certainly solar PV has-been and will continue to-be important for space exploration, but I think rocket fuel made from biomethane is extremely unlikely.

Unlike Earth, Mars has no clouds.  The Lunar destination for NASA's upcoming Artemis mission is a part of the Lunar south pole that has sunshine for most of the year.  So these two locations are great for solar energy (I'll ignore the more important areas of the Lunar south pole, which have water-ice, a crucial resource, but are permanently shaded, because of the many areas of Mars with both daily sunshine and water-ice).

Solar PV panels can range between 20% efficient (affordable Earth-bound units) to 40% (super expensive space-grade units).  In comparison, bioenergy is typically an abysmal 2% efficient at converting light to electricity.

Of course electricity can be used to make rocket propellant from water and Mars's CO2-dominant atmosphere, at very high efficiency (>50%).

For a great discussion on making rocket propellant on Mars, and many other Mars exploration issues, I recommend Robert Zubrin's book,  The Case For Mars.  It's from 1996 (pre-SpaceX), so its attachment to a system resembling NASA's SLS rocket may seem a little dated.  But it is still a great intro to Mars exploration.

Algae and/or hydroponics systems may someday be a part of closed-loop life support systems however.  NASA of course, has demonstrated chemical systems that can recycle water and air on space stations (with clean water and oxygen as the products, and methane as the waste).  But algae and hydroponic systems may turn out to be the simplest for adding food production to the system.

Alan Rozich's picture

Thank Alan for the Post!

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