At the moment, you would need to contact each company, get their requirements that you must meet, and estimated sequestration/dollar return. Don't forget that at the moment trees, and yes soil sequestration as well, are long term commitments.
Ask the question - who looks after the project after 30 years? We will be looking at each of them as well, and give some factual information on what they offer. Keep your eyes on the website - www.carbonfarmersofaustralia.com.au