If you cut down and burn trees that take 50 years to grow in 3 seconds, you've increased the amount of CO₂ in the air. Sure it will eventually go away, but the thing that causes climate change is the CO₂ being in air at elevated levels, even if it's in a cycle.

Biofuel is almost as bad as fossil at 230 gCO₂-eq/kWh. [1]. Compare to solar pv at 40 and nuclear at 12.

[1] https://www.ipcc.ch/site/assets/uploads/2018/02/ipcc_wg3_ar5...

The footnote on those numbers says:

> Direct emissions from biomass combustion at the power plant are positive and significant, but should be seen in connection with the CO2 absorbed by growing plants. They can be derived from the chemical carbon content of biomass and the power plant efficiency. For a comprehensive discussion see Chapter 11, Section 11.13

https://www.ipcc.ch/site/assets/uploads/2018/02/ipcc_wg3_ar5...

> have led to strong forest Carbon sinks in many OECD regions (Pan et al., 2011; Loudermilk et al., 2013; Nabuurs et al., 2013; Erb et al., 2013). However, the capacity of these sinks is being reduced as forests approach saturation (Smith, 2005; Körner, 2006; Guldea et al., 2008; Nabuurs et al., 2013; Sections 11.2.3, 11.3.2). Active forest management, including management for bioenergy, is therefore important for sustaining the strength of the forest carbon sink well into the future (Nabuurs et al., 2007, 2013; Canadell and Raupach, 2008; Ciais et al., 2008), although countries should realize that for some old forest areas, conserving carbon stocks may be preferential, and that the actively managed forests may for some time (decades) act as sources.