sun's energy converted into biomass?


by Geordie Ross
Tags: biomass, converted, energy
Geordie Ross
Geordie Ross is offline
#1
May6-13, 12:57 PM
P: 9
Does the energy from the sun get converted into biomass? If so, how much extra weight is added to the earth every year?
Phys.Org News Partner Physics news on Phys.org
Physicists consider implications of recent revelations about the universe's first light
Vacuum ultraviolet lamp of the future created in Japan
Grasp of SQUIDs dynamics facilitates eavesdropping
mfb
mfb is offline
#2
May6-13, 03:14 PM
Mentor
P: 10,840
While some small fraction of the solar radiation is stored in biomass, this is released again after the death of the organisms. The net effect is zero, if you neglect fossil remains (which we burn in significant amounts currently). Note that solar radiation does not create new matter - the atoms were there before, too, the sun just adds a bit of energy.
QuantumPion
QuantumPion is offline
#3
May6-13, 03:21 PM
P: 735
I think he is referring to the mass defect of complex molecules created by biological processes compared to the mass of the raw constituents the Earth would have without life. Basically, if you take a balance of the energy received vs. the energy emitted by the Earth, there will be a tiny difference due to the energy stored in molecular bonds.

DEvens
DEvens is offline
#4
May7-13, 10:32 AM
P: 59

sun's energy converted into biomass?


Quote Quote by Geordie Ross View Post
Does the energy from the sun get converted into biomass? If so, how much extra weight is added to the earth every year?
Well... Kind of.

Biomass refers to the mass of biological organisms in a particular area. The area does not have to be geographical. It can be, for example, the plants in a forest as compared to the animals in the same forest. Or the pine trees as compared to the maple trees in a forest. Or the termites in a termite nest as opposed to the other organisms.

Total biomass on Earth is many billions of tons.

As others have pointed out, the sun's energy, even when captured, will produce a tiny effect. Recall the equation e=mc^2. So to get 1 kg of mass you need 9E16 Joules of energy. Plants are about 1% efficient fixing solar energy. The Earth presents a disk to the sun of about 6000 km in radius and the solar constant is about 1 kW/m^2. And quite a bit of the planet isn't green plants. So the mass gained is something less than 0.1 kg/s. This is to be compared to the mass of all living things on Earth, which is extremely large in comparison.

Also, as others have pointed out, this is (very nearly) equal to the heat losses from the Earth. If it wasn't, the Earth would be heating or cooling to match. (The differences is primarily down to energy stored as biological material like coal, peat moss, limestone, etc., plus some changes in temperature.) So the net is very nearly zero.
Geordie Ross
Geordie Ross is offline
#5
May7-13, 05:01 PM
P: 9
Interesting, thanks. Does the earth gain more energy from the sun and geothermal heat than it looses overall?
russ_watters
russ_watters is offline
#6
May7-13, 05:17 PM
Mentor
P: 22,007
The Earth is pretty much in thermal equilibrium.


Register to reply

Related Discussions
How matter converted into energy? Quantum Physics 7
Kinetic energy is converted into electrical energy. How exactly? Introductory Physics Homework 1
Electrical Potential Energy Converted to Kinetic Energy Introductory Physics Homework 2
Potential Energy converted to kinetic energy Introductory Physics Homework 1
Energy can only be converted... General Discussion 5