First, are soy inks really made of pure soy products? If somebody says yes, that is a mere misconception, literally ink products composed of oil, pigments, resins and other various components that makes an ink material. Certainly it's a soy based ink, but not purely made of soy. Carcinogens are also required to produce ink products, a mineral pigment used for black color inks.
Aside from the fact that inks commonly comprise of renewable materials, there are also a few components required in the process of making this material that can't be renewed easily, one good example of which is petroleum. Although there were ink products emerging in the market that claimed to be made of organic materials, petroleum in ample amounts are still considerably added to ink compounds.
When comparing the actual volatile organic compound emissions of conventional ink products over soy-based inks, there's still an argument with regards to this matter. Soy is considered a vegetable, and oils that come from vegetable products when cross link tend to dry out, during the process it emits volatile organic compounds. But given those ideas, conventional inks used in many printer nowadays can still emit and produce more volatile organic compounds.
Printouts made from soy-base inks aid better paper recycling, a line that anyone of us might have read from most articles talking about soy ink products. There's an accurate study conducted with regards to this assumption, a laboratory study from Midwestern University proved that soy-based ink can be easily remove from paper pulp during the recycling process. However, during the study they only used a 4 week old printed material, while based from another study, it reveals that soy inks when aged onto the paper pulp, it penetrates stronger which makes it harder to be removed.
Soy-based inks are biodegradable, but are they really the most convenient option when it comes to environment-friendly printing? Sustainability wise, the answer would probably be yes. But it is just the ink that was re-invented, how about the cartridge which is more concerning. As we all know, printer cartridges are made of plastic components, and to be able to manufacture plastic, non-renewable and minerals are used and consumed. I think instead of debating about the real deal between soy inks versus conventional inks, it would be better if we put more attention on the recycling process of the material from where the ink houses.
If you're asking what could be the most possible environmentally-efficient printer consumable, how about we combine vegetable-based inks with recycled printer cartridges, that would be far more greener. Recycled eco-friendly toner cartridges, ink cartridges and other remanufactured printer supplies are all beneficial for the environment.