This would be a significantly better project than bitcoin, and it would be possible, it just wouldn't serve the same purpose. What it would do is value time and

This would be a significantly better project than bitcoin, and it would be possible, it just wouldn't serve the same purpose. What it would do is value time and effort; what it wouldn't do is waste pointless cycles and energy to make hidden currency. This currency would be valuable because someone put energy toward social good. In contrast, bitcoins are valuable because there's a limited quantity of them and their usage can be hidden. Hence, limitless "bitcoins for good" could be created, in a vibrant and dynamic economy, while highly deflationary bitcoins will simply sit in a miser's coffee can buried in the backyard.