While this is a numbered list, we love all of these ideas equally. So, last but not least, a potential solution to a problem that 2.6 billion people have to deal with: no access to a toilet. Designed for use sitting, squatting or standing, the single-use, biodegradable plastic Peepoo bag is lined with a urea-coated gauze layer that disinfects all waste. Used bags are odour-free for at least 24 hours and are safe for burial underground. Within two to four weeks after use, their contents are converted to high-quality fertiliser—something that's also rare in many areas and could become a source of income and further enrichment for individuals or villages.