I’ve given some more thought to my option for a simplistic evaluation mechanism @NickAzer and it seems unlikely that a simple, conventional, approach would be good enough. Even state of the art, detailed, models have limitations.
So here’s an unconventional, thinking out of the box, type approach that may be a useful addition (irrespective of the level of detail used in the evaluation). Revisiting the circular / recycling diagram made me wonder if we could add additional criteria to the challenge that mean the evaluation is a little easier, whilst still allowing a broad range of solutions across various contexts.
What if we specified a closed system that was fully dependent on effective recycling of all (key) resources?
Nothing is perfect and we couldn’t recycle 100% of resources over the long term. So we might specify the recycling of a percentage of all the key resources (e.g. at least 95%). Typically, recycling requires an area of land (e.g. compost heap, digging organic waste into the soil, or allowing the species within an ecosystem to break it down naturally). So a proposed solution might be required to demonstrate this aspect of the overall process, or at least account for it using accepted evaluation practices. In other words, a real solution would require land use for the growing / production and the recycling. We would also want to be mindful of the process’ impact over time, e.g. on soil quality, biodiversity, and other aspects of the environment (local and global).
We might also specify that solutions should provide and support the highest quality ecosystems with good biodiversity [perhaps based on the best native examples within each region currently, or over the past 100 years]. So land use might include areas for growing / production, recycling and rich ecosystems. [Note: a smart solution might be able to combine all three modes homogeneously.] This means, for example, that if land use changed to agricultural use under this new approach that the land might benefit from enhanced levels of ecosystem quality and biodiversity - depending on what its previous state was.
For example, changing desert in this way would offer significant benefits. (However, implementing the solution in virgin rain-forest might see a net lowering of ecosystem quality, but still experience a better level than today’s approach of slash, burn and mono-culture plantations / livestock farming. But perhaps rain-forests should remain as protected regions anyway.)
Similarly, new solutions deployed in urban areas would be expected to bring those benefits of enhanced levels of ecosystem quality and biodiversity.
In a traditional sense, allocating only part of the “agricultural” or urban land to the growing of food (and other parts to high quality ecosystems) is economically inefficient and sometimes unfeasible. So the innovative challenge here would be for XPRIZE participants to find out how to provide all of these benefits in a way that is socio-economically and environmentally sustainable. Those solutions might be different for different contexts (urban, rural, desert and at sea).