Look for someone to patent that idea….

Low-grade heat is the devil for harvesting energy, and that’s
not through lack of trying. 

Seebert devices are spec’ed in miilivolts or microvolts per
degree, and 20C goes nowhere.  A 300
degree temperature difference is needed to do something useful.  Still not much power in them though.  That’s got to come from somewhere. 

If it worked, it would be like sitting on a block of ice.

Just be thankful he didn’t put a biogas generator in the
seat!

A negligible amount of energy is dissipated from walking on
a carpet, and for this reason the piezo fibres would not be able to generate much
power, even if they were to exist.

When a usable ‘plant-microbial fuel cell’ exists, we can
discuss how much energy it can capture from indoor ambient light.  I’m guessing less than a PV cell.  That’s because photosynthesis reactions are fine
for capturing electrons for slowly building plant material, but are not as good
as semiconductors at outputting electricity (and there’s a reason why we put these
on roofs).

The Seebeck effect creates a voltage proportional to temperature
difference.  The difference between body
temperature and ambient is small, less than about 20C, so negligible power can
be generated.  If thermal energy could be
extracted, it would make the seat feel very cold.

And before energy can be captured from the heat of the
electronics on the desk (see http://www.edditornberg.se)
something has to power the electronics.  Something
other than perpetual motion.

Before hypothesizing energy harvesting, check how much energy
there actually is in the environment that can be captured.  Do the arithmetic.  Think about it.

Please don’t just label a carpet, pot plant, chair and desk as
magic energy generators and imagine that our problems are solved.