Plastics are considered essential materials in today’s society, but throughout their life cycles they contribute to pollution and depletion of non-renewable natural resources. Bio-based plastics appear to be more environmentally friendly materials than their petroleum-based counterparts when their origin and biodegradability are compared. But which of the bio-based plastics currently on the market or soon to be on the market are preferable from an environmental, health, and safety perspective? This analysis found that none of bio-based plastics currently in commercial use or under development are fully sustainable. Each of the bio-based plastics reviewed utilizes: genetically modified organisms for feedstock manufacture and/or toxic chemicals in the production process or generates these as byproducts, and/or co-polymers from non-renewable resources. When deciding to substitute conventional petroleum-based plastics with bio-based plastics it is important to understand the flow of these materials and their adverse impacts in all parts of their life cycles in order to select a material that is more sustainable.