Sustainable Farming

Any thing that is or could be produced using sustainable methods can also be made using non-sustainable methods.
But you want to know whether a given product has been produced by sustainable means, and then you want to know if it is available to you. Those are not the same question.

It would be very difficult to say what is available to you, and from what sources. Next there is no certification for sustainability the way we have for organic production, so if you want sustainable, we got sustainable, but no independent certification of that.

It is common misunderstanding that sustainable farming is subsistence farming and cannot be commercialized. Sustainable agriculture simply means agriculture practices that deliberately reduce external inputs (such as synthetic agrochemicals and fuel) and replaces these inputs from within the farm and from natural resources. Some sustainable agriculture practices are intercropping, crop rotation, organic farming, minimum or zero soil tillage, agroforestry, zero burning, integrated pest management (use of organisms to control pests and diseases), natural soil mulches, composting, cover crops, and green manure.

It really depends on the farm. A large certified organic farm probably uses almost as much petrol as a conventional farm-plastic for greenhouses, row covers, mulches, buckets, packaging, fuel. They do not use petrol based fertilizers, pesticides, etc., though. A farm that uses animals for traction and does not use much plastic would be quite sustainable

It also depends on if the farms raising both livestock and crops as this makes a farm far more sustainable than a farm that raises only crops and has to import in compost/aged manures.

Smaller human scale farms tend to be able to do the sustainability thing far better than the large machine scale industrial farms

But some things that all Organic farms do that are sustainable-growing soil, not using petrol based inputs, encouraging beneficial insects and other animals to live in the farm eco-system, recycling waste products such as manure, crop residue, harvest waste, spent produce back into the farm system (composting, feeding to livestock), growing cover crops to ward off erosion of the soil as well as to feed the soil, etc..