Ken Fabian

SpaceX may not end up with the re-usable giant rocket they envisaged - I will be surprised if they do - but they could very well end up with a useful heavy lift system, to service Near Earth space activities and launches of bigger and more numerous robotic probes/astronomical instruments - which may always have been the realistic rather than dream goal for the company. Improved tunnelling technology for the HyperLoop company, but not necessarily the grand dream transport system. Could well be that within these companies that, whilst certainly in their thinking, the extreme successes have never been expected, nor even necessarily their principle goal; it gives these companies a big PR boost and lots of public interest. There are things still to do in space, including closer examinations of Mars and moons of Jupiter and Saturn looking for evidence of past or present life. Cooperative efforts to develop meteor defence - or uncooperative efforts to militarise space seem to offer more realistic near term possible opportunities for a space tech company - although I would not welcome the militarisation; if nothing else that suggest moving towards the kind of world that is still not managing it's big issues effectively (and possibly handling them worse as things like climate instability start to bite). I do think a stable, healthy Earth economy is a requirement for some of the more ambitious space enterprises, to both kick off and succeed. And, yes, there are the valuable on-world explorations - including the very small, like the astonishing and still surprising biochemical machinery of life, which looks profoundly important to future agriculture and medicine, and things like the complex nature of films and surface interactions, that may deliver much improved electrical devices, energy storage and efficiencies of use.

Musk is dreaming - the timeline he has proposed won't work. With technologies within his/our reach, a Mars colony is not going to be viable. I don't know when or even if we will put people on Mars. It would be a notable achievement but not necessarily something that leads to where you think it will go. I see nothing inevitable in Mars colonies nor any great loss if we don't end up with them; when all is said and done it's a wasteland and the opportunities there are greatly exaggerated. The potential for being a viable backup planet in case Earth is rendered uninhabited is, with the real technologies within reach, unreachable. The threshold size for true self-reliance under such conditions is, I think, going to be that of a substantial nation, population and economy. I think that can only be an emergent outcome from a long history of being a successful - economically successful - outpost. If it isn't economically successful as part of the Earth economy it will fail to thrive and self-reliance will not occur - to become one more ghost town in one more place that began with high hopes.Terraforming Mars is just fantasy. Maybe we will get good at living in wastelands - but I think our technology will have to be extraordinary to be able to have a productive, advanced economy and society somewhere as desolate and unforgiving as Mars. That level of capability would make space habitats possible, in which case, why Mars at all? I think you saying the political and economic concerns are temporary and will change is one more example of wishful thinking - hype - and does not address the practical concerns I have raised with Musk's Mars ambitions - from the proposal to run things on solar when months long, planet wide dust storms are a regular occurrence to how such a colony, that can't even engage in return physical trade, pays for the continuing supplies they will require, they go unanswered.

It seems to me you are saying you think attitudes like mine have stood in the way of progress since pre-history. That could not be more wrong and completely misreads the nature of the issues I have with this and other grand space dreams. It's not like me objecting to a Columbus using, existing, proven technology to try to reach India, but more like seeing someone with a bark canoe proposing it and me shaking my head at it. Except across this 'ocean' there is a desolate wasteland on the other side - we already know that; exploration has been ongoing for some time. It doesn't make sense to me attempt to plant a colony on Mars, no matter how I look at it. You could try addressing some of the issues I've raised for why I think that rather than making this about my lack of enthusiasm for what looks like serious overreach. Colonising Mars is overreaching. There is plenty of room for goals in space and on Earth that are not overreaching and still advance us significantly and I support most of them. Even Musk and SpaceX can be extremely successful and never develop the BFR as invisaged; if they end up well short of that and don't ever do the Mars missions, but still develop a bigger than before, reusable launch vehicle that lowers costs to LEO that can be a great success. In that sense, sure, the overreach can still land SpaceX further along in bringing down space launch costs - except that I don't think it will be the overreaching of ambition that is the crucial factor that delivers the results, or believe that aiming a bit shorter, say just aiming for a big, reusable launch system without the Mars hype, could not deliver the same.

The line between government and commercial gets blurry for things like communications satellites when governments are major shareholders and guarantors in commercial ventures, but, yes, I may well be wrong about how much taxpayer money is involved. Near Earth activities do have a large commercial component. However, activities that go beyond near Earth, that are not driven by revenues from customers on Earth will tend to be more taxpayer funded than genuinely commercial. But this is not my principle problem with plans for colonising Mars. Colonising Mars is a lot bigger undertaking. There is not a Cold War arms race to spur things along and justify taxpayer spending this time. I find myself incapable of unquestioningly sharing the optimistic enthusiasm - I have material concerns that make me question the feasibility. Like Mars colonies, asteroid mining is currently and for the foreseeable future, far more hype than substance, again. Grand space dreams are full of it. Estimates of enormous value in precious metals like platinum contained in metallic asteroids are almost certainly based on their presence in nickel-iron meteorites. Over 100 ppm of platinum group metals in some samples, mostly associated with the nickel (higher nickel content, higher platinum content). As placer deposits on Earth that would be "WOW". As a trace component of nickel-iron alloys it is not. Alloys of metals are easy to make, but unmaking them is very difficult; extracting platinum from nickel-iron would probably be a challenge for a refinery in the middle of a major industrial district on Earth. Even separating the nickel from the iron by means that are economic will be challenging - and there is no reason to think we will find pure iron or pure nickel. On the contrary, all the meteorite samples known have nickel-iron mixtures. It is not only vastly improved space technology that has yet to be developed. Nasa's Osiris Rex will, at best, return 2 kg of asteroid material, at a cost of US$1 billion. $500 billion per metric ton. Pig iron sells for $400 per ton. Delivered to a sea port of your choice. Nickel is worth more - $15,000 per ton. Platinum a lot more - $26,000,000 per ton. Of course it won't be - can't be - done anything like Osiris-Rex, but then, we don't know how to do it, except as vague hopes that every kind of technology will have improved enough. One day. There is no viable means to mine asteroids. Dreams, not plans. Hype, not substance. My own view is that asteroid mining will need to be based on bulk commodities not precious metals, beginning with delivering minimally processed crude nickel-iron for lower cost than any Earth based supplier of nickel-iron alloys. Under $5,000 per ton? Probably needs to be cheaper than that. There could be pleasant surprises - rarer materials that have high value. Actual mining projects will still need to be based on what is known, not on hopes like that.

No, I am not saying that we should sit on our hands - but I do think the kinds of technological advances that make real differences are no more likely to come from trying to go to Mars than from broad, ongoing support of R&D here on Earth. Less likely, because Musk's Mars efforts will be a tiny part of overall R&D, and the breakthroughs needed to make Mars colonies work are not in refining the technologies we have, but true breakthroughs - the sort that don't come on demand. My unwillingness to cheer this project on is not unthinking Luddite style resistance to change. We went to the top of Mt Everest - but I don't consider the adventure tourism that has arisen there any kind of valuable advance for humanity. Please don't mistake landing on the moon for opening up new opportunities for living on the moon - it hasn't delivered that, not because of lack of optimism, nor even excessive pessimism; rather, it is based on realism. Exploring is fine, I support it, but not unthinkingly. I have reasonable expectations of what it will deliver - and those are not great colonial opportunities. Colonising Mars, however, is not any kind of genuine opportunity. I'm not convinced it is even valid and worthwhile or even counts as exploration as such, even if it will likely incorporate some. How things turn out in the future is up for grabs, but a failed Mars colony - and I think this attempt is doomed to fail, likely in the actual nuts and bolts planning, hopefully not in the execution - is as likely to be the pivot point that brings home the reality of how difficult space actually is as be the inspiration for grand space visions.

We are still 'stagnating on planet Earth' and this project will not change that. Landing on the Moon did not change that. Missions to the Moon showed us that it's a desolate wasteland, without exploitable resources or opportunities. It wasn't lack of enthusiastic optimism that stopped a Moonrush in it's (nonexistent) tracks - reality, not value judgements did that. Mars is no better. Rather than criticise my lack of enthusiastic optimism - honestly, I don't think this project deserves it - perhaps people can explain how this can possibly deliver any kind of viable colony. I don't think it has any reasonable prospect for anything but shortest of short term survival. And I don't see any compelling, achievable reason to do it. So - There isn't a BFR yet. A BFR that can put 100 tons into LEO will deliver a lot less than than to Mars. Less again if they are expected to have sufficient fuel to lift off again and get back to Earth for another trip. Or more trips to put in place the supplies to lift off again. Still no clear way to protect against radiation, either during the trip or on Mars - building underground is not going to be a simple matter. Perhaps ice or ice bonded gravel, but these still need equipment, materials, energy and labour. Utilisation of local resources is going to problematic - equipment, imported material, energy and labour. No clear plans for reliable energy supply - which will not be able to rely on solar alone due to periodic, long duration dust storms. A Mars rated nuclear plant, like so much else, does not exist. How does the colony pay for the repeated resupply it's medium term survival will depend on? What are the economic underpinnings? I think the lower gravity will hinder as much as help; it provides traction. Working in space suits will hinder and slow every normal activity; physical work will be a lot less productive than Earth equivalent. Reliance on robotics and remote devices add a level of complexity, not reduce it. No, the problems are not primarily any lack of enthusiasm by people like me - the problems are real and substantial. I am not stopping Mr Musk - I think reality will stop him. I suppose the ethics of promoting something that isn't going to work requires disclaimers. I would presume there are intentions for use of BFR's that do have genuine commercial prospects - although like a lot of 'commercial' aerospace activities, those rely heavily on government contracts, ie taxpayers ultimately footing the bill. Increased militarisation of near Earth space looks possible. A new, bigger space station perhaps. Asteroid mining presents a whole lot of other difficulties so probably not. Some kind of unique, high value, only in zero gravity products might move space stations beyond subsidy to profitability? But we haven't seen any so far. It isn't optimistic enthusiasm that is lacking, it is evidence of actual, near term economic opportunities - and Mars doesn't have them.

No, I think it is an ethical, economic and financial judgement. Economic and financial because it makes no economic or financial sense. Ethical for promoting it when it makes no economic sense. Someone wants a science base, it is funded on that basis - not on the basis that it's going to be a backup for Earth or can be financially self-supporting or great entrepreneurial opportunities await the colonists.

Musk is dreaming. Along with most of the people posting here IMO. As thought experiments Mars colonies can be fun, but expectations of making them real are greatly exaggerated. The reality is likely to be life and death serious without so much fun - living in a bunker with the planet outside trying to kill them. Absolutely reliant on equipment and supplies that come from another planet. I think the whole enterprise is based around excessive and unrealistic hype, which is itself based on taking science fiction fantasies much more seriously than they deserve - fiction which routinely understates the difficulties and overstate the opportunities. There is no opportunity on either Mars or the Moon that is worth this effort. The difficulties remain enormous. The safety margins for every bit of engineering have to be better than here on Earth, not something shorted on. There is no prospect for tradeable commodities but the ongoing need for high value equipment and supplies will remain great. No clear business plan exists beyond charging people to participate - and "entrepreneurial opportunities" will be very difficult to create. There is no independent space economy or in-space market - if it doesn't work and pay it's way as part of the greater Earth economy it doesn't work. Mars or Moon colonies will be far more at risk of extinction events than Earth, even if they are sufficiently large to have a working, advanced industrialised economy - and that is, I think, the minimum threshold for self-reliance. They won't be a safe haven for preserving humanity until their risks of being wiped out have been reduced near to those of Earth's; I just don't see the backup humanity motivation for underwriting Mars missions as anything but misleading - way too far off in needed capabilities, in time, in space to be meaningful. Earth will need to backup Mars for a long, long time and, whilst the media exposure means we might make much greater efforts to help if (when) things go badly awry than we would for any of the tens of millions on Earth in desperate circumstances, that kind of generosity of spirit has limits, especially for people who knowingly undertake high risk activities. The tech advances to make it more viable will not be local Mars ones - only large wealthy economies can support R&D at that level. Reliable energy supply has not been adequately addressed. Can't run a Mars base off solar alone - dust storms last for weeks and months. Nuclear, maybe, if it can be done with radiative cooling rather than water or air cooled. Not something a stranded colony is likely to be able to do much to make or even fix if it goes wrong. More than one nuclear plant, for redundancy and parts for another? A team of nuclear technicians and engineers - and an extraordinarily well equipped workshop? Perhaps on the Moon linked solar farms circling the poles could provide reliable supply - but that's a major engineering enterprise, something that will come when colonies are already successful at large scale. Cart before horse? And who is paying for all this? What are the real economics? What expectations of repaying the investment the enterprise costs could Mars or Moon colonists have? Tritium mining is pure fantasy - most of the few kilograms of annual demand for the stuff is for nuclear weapons; we are yet to get a working Deuterium based fusion reactor and those based on Tritium are much harder. Cheaper - like pretty much everything else - to make Tritium on Earth. The only income streams for such colonies look like the media broadcast rights - but if a colony is reliant on being a popular form of reality TV show it is already in trouble. Quite frankly I think the whole exercise is far more TV fantasy based than soundly based on realistic objectives. Dreaming I says.

My mistake - Phi for All and Swansont can speak for themselves. I would expect most scientists actively seek to avoid reliance on questionable assumptions - and whether it accompanies the process of writing up their work for publication or preceded it (during their education) a lot of questioning goes on, unremarked. I think the extent of questioning of science's assumptions is sufficient; "always" questioning them can be wasteful of time and resources.

I think that is a matter of interpretation - although it is quite possible my views on this do not align with Swansont's; that does not mean you have shown that significant mistakes are being perpetuated within "science" or are being concealed or go unaddressed when they become known. This a forum, not a science institution; I'm offering my opinions, as is Swansont. You do not win this argument because Swansont and I don't agree - (The Fallacy of the Fallacy). Working scientists operate within codes of conduct, with expectations that standards for professionalism - including honesty, accurate record keeping and logical consistency - are adhered to; careers can be ruined by failures in these areas. My main point is that science that gets used all the time gets questioned all the time - not only by scientists questioning their assumptions and attempting to find mistakes in their own work (if only to avoid having them pointed out by others) but by the consistency or lack thereof with existing theories within their results. This kind of questioning does not have to be emphasised or even mentioned within published results to have taken place. You can find areas of science which don't get used widely and the extent to which they are subjected to critique can be limited by their obscurity and the small numbers of scientists engaged with them. Or find subject matter where fundamental questions remain unanswered and competing schools of thought exist. Such levels of uncertainty do not usually go unacknowledged or unquestioned - more often the first thing they will say is they don't know. I would note that the examples of science getting things seriously wrong and scientists getting stubborn about it have mostly not occurred in recent times. They are almost all examples of better grounded understandings ultimately displacing those erroneous positions, ie of science asking questions and working. It is not only the body of knowledge that is science's product that has grown and improved; the systems and practices science is conducted within have grown and improved too.

If there is no evidence that existing science based understandings could be wrong there is not a lot to question. When such evidence arises it tends to get addressed - and such evidence does get noticed when it arises; scientific careers can be made out of it. Is the evidence valid and significant enough to overturn existing understandings? How do you know? When scientific understandings are widely applied the opportunities to notice things that don't fit are increased, not decreased; it isn't a matter of constant, deliberate searching for things that don't fit - they are an inevitable outcome of using theories that are wrong. If you make your own personal judgement the basis for accepting a theory as valid - and make your not understanding (or remaining unconvinced) the basis for your rejecting it then you are on very shaky ground. Appeals to authority may be a genuine logical fallacy, but presuming you know better than the experts is a fallacy too and it is the fallacy of the fallacy to think appeals to experts make the experts wrong. What sources have you looked to? Do you have competency in the skills needed to make sense of complex arguments? Do you expect random people on internet forums to convince you and do you claim a widely accepted theory is false if they can't? Perhaps their comprehension is lacking, or perhaps yours. Perhaps they are not very good at explaining. Perhaps they are not able to penetrate a fierce determination to admit no mistake or any lack of comprehension or deviate from an existing belief. Perhaps you need to have the skillset that comes with years of undergraduate study followed by years of post-graduate research.

DexDX, Perhaps it is in the evaluation of their relative significance that valuable lessons could be developed and looked at by students. Which problems have the greatest potential impacts? How do you weigh between problems that will revert to their earlier state when you stop doing "x" and those that leave enduring changes when you stop? Which problems depend on and interact most strongly with other ones and which tend to stand alone? I keep thinking of those Venn diagrams, showing which overlap and which don't. I don't know what age or skill abilities and these are questions that push experts working in teams to their limits, but I do think an attempt to give an overview could be worthwhile.

There is a lot of overlap between many of the problems listed. I tend to focus on climate change as the most pressing issue, because it is cumulative, effectively irreversible and within our reach (technologically) to take effective action. Our single most abundant waste product is CO2 - I did a rough calculation for Australia and got 6 times more CO2 than all other kinds of waste combined (of about 20 tons of waste per Australian per year, 17 tons are CO2). Of course climate change relates to population, however I think that education and improved prosperity tends to lead to greater use of birth control and reduced population growth - although I do wonder if this is in part an unexpected consequence of modern consumer society's embracing of selfishness. Why have lots of kids when you will have more to spend on yourself if you don't? I'm sorry that I can't provide anything substantial to help you develop a suitable study program. I'll be interested to see what responses your request gets.

Much as the NAS papers - which greatly differ in their conclusions - are about the intersection of technical capabilities and economics as energy production approaches 100% low emissions, this argument simply drives the debate into the same old ruts where nothing gets decided. For some players in this, doing nothing (which is actually the continuation of doing planet altering unconstrained emissions) is a desirable outcome. A link to the NAS evaluations would have been better than the link to Shellenberger's take on the NAS evaluations; frankly I'm not convinced he or his Ecomodernists are sincere enough about the climate problem to be even handed and look unlikely to ever switch from being relentlessly critical of Environmentalism and renewable energy - a theme which has the support of pro-fossil fuels conservatives - to being relentlessly critical of climate science denialism and the continuing amnesty fossil fuels enjoy with respect to externalised (climate) costs, which does not. Shellenberger does not strike me as any kind of non-partisan player - and when push comes to shove, I think he will support the fossil fueled status quo, with economics as justification, rather than commit to emissions reductions by means that he does not support. Nor does he offer a path to actually doing emissions reductions by the means he does support, primarily with nuclear - and so long as climate science denial has it's insidious hold over the imaginations of conservatives (who like nuclear) the main block of existing political support for nuclear will not be mobilised to displace fossil fuels. Taking pro-renewables Environmentalists out of the political game - and I think that is what Ecomodernism seeks to do - will not, in my view, lead to any genuine, new commitment to doing emissions reductions with nuclear. It's the same old renewables versus nuclear fight, yet again and that is a great distraction from the main game of renewables and nuclear versus fossil fuels. Frankly I think anyone who thinks they know how we will manage the end game of reaching very low to below zero emissions and how much it will cost is kidding themselves first, along with everyone else; making those projections or predictions the basis for our near term choices for the interim targets - getting to 50% or to 80% - can become quite limiting of our options. There are now firm plans for pumped hydro installations as well as a lot more RE projects that include "firming" via batteries; we should see how well they play out. Let our experience of them in practice guide our future decisions. Certainly South Australia's recent experience with large batteries has been very successful, and they are already moving past 50% renewable electricity.

Possibilities are not unbounded or unconstrained; not everything is possible. However, as long as a full and true understanding of everything that is relevant is not known, we are "free" to imagine possibilities that won't be true. The more we do understand the easier to recognise and dismiss "possibilities" that are illusory. Humans have evolved to be able to survive, to reproduce and support their offspring to survive and reproduce. With a social species the ability to support and assist those around them to survive and reproduce contributes to the individual's ability to survive and reproduce. The details of what individual traits contribute can get very hard to pin down; in one circumstance the ability to whack at others with clenched fists will be a valuable survival trait. In another, the ability to make a spear that flies straight and has a point that can penetrate flesh will be a determining factor for survival; the one making the spear need not even be the same one as throws it. It gets very complex to tease out what individual traits contribute to that first "function", to survive and reproduce.

I agree that Greenhouse agriculture doesn't suit all crops and crops like wheat are unlikely to be grown that way. But where wheat or other broad-scale crops are grown using irrigation - most wheat isn't - it is done because the availability of low cost, bulk water makes irrigation possible. I'd expect iceberg water to only be for high need, high value situations - municipal water, industrial processes or intensive, water efficient agriculture. Which competes with options like desalination. The problems look significant. Much municipal water infrastructure will be unsuited to repurposing for extraction and storage of iceberg water. I would probably count on having to invest in significant, dedicated infrastructure. If I were really serious, I'd consider some kind of sea level pondage in the style of a ship's dry dock - float the iceberg in, close the water gates, pump out the sea water and let it melt in place.

Getting the ice to a suitable bay or port isn't the end of the story. How do you get the iceberg water from it's mooring to where it is to be used? Significant infrastructure at the port and pumps and pipes to suitable land based storage seems necessary. I'm not convinced this is going to be a cost effective means of supplying water - or that supply of fresh water is the critical element to enable agriculture in places like arid Australia. Greenhouse based cropping, with solar power and thermal desalination of sea water appears to be working effectively in South Australia. Very efficient water use and solar powered climate control appears integral to the success of Sundrop Farms. I doubt the desalination is the biggest issue or expense. The same company has - or plans - more of these, in the USA and Portugal as well as more in Australia -

Been a long time since I did circular motion in (high school) physics classes but I don't think this could exist as a steady state; change the axis and precession results. There is a lot of momentum in a spinning planet that will resist changing the axis.

Estimates of how much CO2 humans exhale vary and I have not had much success finding accessible published scientific papers for this. From a media article that got it's numbers from Jay Gulledge of the Pew Center on Climate Change - 2.3 pounds per person per day or 840 pounds per year. In kilograms (which I am more accustomed to) about 280 kg per person per year. I've seen other figures around the 400-500 kg per person per year. The food that the carbon came from would have directly or indirectly drawn that from atmospheric CO2 via plant photosynthesis - and as such should not effect atmospheric CO2 concentrations. However, the contributions of fossil fuels to the growing, processing and distribution of that food can and will contribute to changes to atmospheric CO2. I agree that the world as we know it will be irreversibly changed by global warming - as well as other human activities. The politics around this issue dismays me - but that is for another thread. I'm not entirely without hope that the politics will shift and that we can regain some degree of climate stability to leave as a legacy - a changed but more steady climate state rather than still rapidly changing. Some effects will continue no matter what we do - a lot of sea level rise over the next few centuries seems hard to avoid now.

Nitrogen - N2 - would be the biggest component of combustion exhaust gases but passes through mostly unaffected. Some NO(x) is produced but only a small portion of N2 that passes through is effected. I was surprised that CO2 exceeds other waste by such a large margin but I suppose I should not be surprised that the quantity of waste CO2 is so great - nothing about this is secret; more like it has been going unnoticed and unremarked whilst in plain sight.

I tried to find better sources for assessments of how much waste we make - again I have done this from an Australian perspective, but expect the overall conclusion won't be much different in other developed nations. Looking at Australian National Waste Report 2016 (the most recent I could find) I didn't find wastewater per se or CO2. It does appear to include 'biosolids' from wastewater treatment - which would be less than if they counted the actual urine, faeces and other materials fed into that wastewater, both because the initial water content of them is not counted and a lot of the organic materials are broken down. Some of that material will be released as Methane and CO2 along the way. The report does take account of methane that is collected and burned (but not that which isn't) as fuel and mentions that it becomes CO2, to be added to Australia's emissions inventory, which, like methane emissions, is not part of the report; it's there as a form of waste treatment - "energy recovery" - alongside recycling or disposal (landfill). A lot more construction waste (726 kg of masonry) than I expected - and had thought was counted as municipal waste but wasn't - and a lot of fly ash from coal burning (760kg) which, given the CO2 emissions, didn't surprise me. I used 15 metric tons of CO2 per capita but it is actually over 17 tons The total waste for an average Australian before recycling, energy recovery or disposal (up to 2014-15) is given as 2705 kg per capita - which makes my previous estimate of CO2 being 7 times more than all other waste combined an overestimate; seems like it is only 6 times more. But that doesn't leave me feeling any better about it.

These are 'back of envelope' type estimates, not definitive. I may have been thinking of daily rather than annual wastewater volumes, so wastewater probably does make up the largest volume of human waste - I'll have to go back and look for the right numbers, but my point is, it is still mostly water. Actual waste content is harder to pin numbers to - 500 litres of urine per person per year. Less than 200kg of faeces. Solid waste for Australians, about 1,500kg. Other waste? There will be some, but it still looks like about 7 times more waste CO2 than all other waste combined. Exhaled CO2 is about 1 kilogram per day or 365kg per person per year, ie 1/40th of an Australian's emissions is from breathing - and as long as we don't count the associated emissions from agricultural production and supply chains exhaled CO2 all came from atmospheric CO2 converted by plants into food to give (approximately) a zero contribution to raised CO2 emissions. The associated emissions from food production don't round out to anywhere near zero though. I don't think I've ever heard CO2 spoken of as our largest single waste product, but unless someone can show my estimates are way off it looks like it is.

If wastewater - usually considered the biggest single human waste product by weight - is waste plus water but we only count the waste, and exhaust gases are air and CO2 but we only count the CO2... would that mean it is actually Carbon Dioxide that is the largest single human waste product? By weight? By volume I suspect it could be CO2 anyway - and more confidently suspect exhaust gases containing CO2 would be more by volume than wastewater. It has struck me before just how much CO2 we actually make, mostly oblivious - a more average Australian than me makes 8,000 cubic metres/280,000 cubic feet of CO2 per year. 180 times my own body weight of CO2 per year, 1,800 times my weight per decade, enough I suspect, to make column of pure CO2 with my body's cross section that reaches halfway to the ISS each year. This is going on largely unnoticed in open sight, through an abundance of exhaust pipes and smokestacks, but it looks to me like CO2 is our single most abundant waste product.

Ah, that makes sense. Mystery solved, thank you.