Solid human waste can be exposed to vacuum, dried or even incinerated in a solar oven. Options that would be energy intensive on Earth would be relatively simple on Mars by taking advantage of the hostile environment. No chemicals required. Then it would be safe to use as fertilizer.
The mission to Mars provides many challenges in vitamin stabilization."You can make food that is stable, but vitamins are biological materials that degrade over time," Barrett said. "Especially if there is cosmic radiation; then they are even more susceptible to degradation. Cosmic radiation can damage vitamins and create more of a need for antioxidant vitamins for the astronauts. This could result in malnutrition."The vitamins need to remain effective and intact during the astronauts' time on Mars, and they also need to remain stable during travel to and from Mars."NASA is also interested in stockpiling food there for subsequent missions, which is why they want a five-year shelf life," Barrett said.
What follows is a thought experiment:Each Martian colonist will eat 2 kgs of food per day. Let's assume that 1.5 kgs are from plant sources, and 1kg is from a higher plant. Assuming for simplicity's sake we use all aboveground biomass and throw away the belowground biomass, and using a harvest index of 0.5 we also have 1 kg of biomass that is inedible to people but potentially available for feed. Now if we use all this biomass as feed (and not say for composting human waste or other such necessary uses) with a feed conversion ratio of 3 to 1 we could have 0.333 kgs of animal. Now, it is highly unlikely that this biomass is a balanced animal meal but let's ignore it for the moment. Now Dr Google is not that great in finding the conversion ratio of animal weight to food but here is a tolerable link:
Algae?How about each colonist eats:- 0.5kg of fish or chicken. These are produced from 1kg of algae.- 1kg of algae, synthesised into flour (bread) and other staple foods / or some other forms of carbohrdrate synthesis.- 0.5kg of tomatoes and lettuces grown under artificial light- A synthetic flavours unit producing trace amounts of flavours to make the above taste good. Total: 2kg of algae and 0.5kg of salad.The challenge really is to make something with the nutritional and taste properties of rice, pasta or potato from algae.
So meat is easy. But still the essential question is how do we turn Algae into the bulk carbohydrate equivalent to pasta or rice or potato, which make up the bulk most people's diet?
Grains on Earth are very cheap, and already healthy. So there's no incentive for anyone to research an algae-based grain substitute. Once off Earth though, it will be essential.
Quote from: alexterrell on 01/18/2016 10:03 amGrains on Earth are very cheap, and already healthy. So there's no incentive for anyone to research an algae-based grain substitute. Once off Earth though, it will be essential.I believe some thought is given to algae as a future staple food for the growing population. However purely scientific basic research, nothing on real application besides adding some algae to products for increasing nutritional value.
You (I think) mentioned algae being used to make flour. Is that the right kind of flour to make bread?
Solazyme released Algal flour in October, and Algae milk is made from this new Algal flour.
Algae are a very efficient producer of both oil and carbo hydrates. Grains I just cannot see in the mix, space and time inefficient. I would bet, calories from chicken or fish fed algae and bacteria protein takes less ressources to produce than grains even considering the conversion losses.But I agree that 500g meat or anywhere near that is not economical. I can and do produce delicious meals with 50g of meat per dish.
In the natural cycle of things, animals produce the manure and urine for fertilizers, which the plants love. Even algae must eat something to produce their oils and proteins. CO2, water, but does algae need something else?
@RobotbeatI am not sure what you are arguing. I argue that algae and protein from bacteria are more efficient than producing staple foods with higher plants like grains and oil seeds. I argue producing a wide variety of products from algae and bacteria will be the base of food production. I think so far we are in agreement.I only add the argument that calories from fish or chicken will still be more efficient than growing staple foods from higher plants. I don't deny that it is less efficient than using algae and bacteria protein directly as food for humans. I just argue that we probably can afford a small amount of animal food using algae as they are very efficient and that people will want it.So the food base will be algae, bacterial protein and vegetables, herbs, spices, that add not so much calories but variety, people will want to have.Plus of course there will be programmers and we know that programmers need coffee. So we need a source of coffee too.
Under most unnatural feeding conditions tilapia are unable to sufficiently ingest high volumes of algae. They may need constant grazing to fulfill their nutrient requirements.[444] Tilapia (Sarotherodon niloticus) grow better on fishmeal (fish meal may contain 74% protein and 8% lipids.[445]) than on a 25% protein green algae meal (Cladophora glomerata). Weight gain decreased as the level of algal protein increased as replacement of fish meal. Protein digestibility was highest on a 5:1 ratio (fishmeal : green algae meal).[446] Protein synthesis (with normal sulfur and carbon content) by green algae during the night may match protein synthesis during the day (in Dunaliella tertiolecta).[447] Protein derived from algae does not promote adequate growth in Rainbow trout.[448] Fish fed 5% ulva meal (Green algae; Ulva rigida) showed increased growth, feed conversion ratio and protein efficiency ratio.[449] Ulva meal may replace soy bean meal to the extent of 20% without negatively affecting growth of male larval tilapia. Feed conversion ratio increased with increasing ulva meal content.[450] Green algae meal (Hydrodictyon reticulatum) may replace meal to the extent of 25% without negatively affecting growth of Oreochromis niloticus and Tilapia zillii fingerlings.[451] Spirulina maxima meal protein can replace up to 40% of the fish meal protein in Oreochromis mossambicus fry diets without negatively affecting growth.[452]
Tank-cultured tilapia can have very efficient feed conversion ratios (FCR). The time period for FCR can be days, weeks, the length of the tank production cycle, or a year. FCRs in the range of 1.4:1 to 1.8:1 are common with tilapia and are some of the best in animal agriculture. While FCR is one of the most important benchmarks for measuring the efficiency of an operation, FCR alone does not give a true measure of production. An artificially low FCR can be created by underfeeding, so it is important to consider the growth rate also.
QuoteTank-cultured tilapia can have very efficient feed conversion ratios (FCR). The time period for FCR can be days, weeks, the length of the tank production cycle, or a year. FCRs in the range of 1.4:1 to 1.8:1 are common with tilapia and are some of the best in animal agriculture. While FCR is one of the most important benchmarks for measuring the efficiency of an operation, FCR alone does not give a true measure of production. An artificially low FCR can be created by underfeeding, so it is important to consider the growth rate also.But as Bawdy et al note at https://ag.arizona.edu/azaqua/ista/ISTA8/FinalPapers/11%20Nutrition/8.%20TARTIEL.doc.At a 75% algae meal, FCR was at 3.24 for Chlorella and 2.74 at Scenedesmus algae.The high FCRs in the literature and at the JSC experiments are with soymeal and the like, not algae. You will need a very balanced meal approach to growing tillapia, including vitamin and micronutrient supplements for the fish in fish available form.I am not in favor of a vegan diet (a vegetarian diet is useless, if you have the animal you might as well eat it). However Mars grown animals except perhaps insects shouldn't show up before significant infrastructure is created. Meat ought to come from Earth.Grains are an integral part of all high quality animal feeds. Chickens cannot grow without grains, cows have bad FCR when relying on a low grain diet. Grains also survive a long time without need for refrigeration or other special storage conditions. I am pretty sure that they will show up quite early in a Mars agricultural system. And yes, algae require nitrogen fertilization.