Beyoncé and Jay-Z are offering fans the chance to win free concert tickets for life – in exchange for going vegan.

Beyoncé on Thursday asked fans on Instagram to commit to a certain number of vegan meals to enter the special contest – and one lucky winner will receive free concert tickets to any Beyoncé and/or Jay-Z show for life.

By Thursday evening the post had received more than 500,000 likes.

The Greenprint is an initiative of the Carter co-owned vegan nutrition service 22 Days Nutrition. Meat-free meals can help in the fight against climate change, and the Greenprint’s interactive website demonstrates the positive impact of going vegan, from absorbing harmful emissions, to cleaner water to the conservation of power.

After a brief slideshow, users are asked to pledge their contribution to the vegan meal proposal. According to her Instagram post, Beyoncé herself has pledged to participate in meatless Mondays and eat plant-based meals for breakfast. Other options include: all plants all the time, plant-based at work, and two plant-based meals a day.

Created by exercise physiologist Marco Borges, 22 Days Nutrition is based on the belief that habits are formed in 21 days, therefore a 22-day diet establishes a pattern that encourages people to stick to the plan.

The superstar couple originally got involved with 22 Days Nutrition in 2013, just before Jay-Z’s 44th birthday. The rapper blogged about the challenge, calling the timing of his start “serendipitous” and “spiritual”. DJ Khaled is also a fan of the service.

Jay-Z and Beyoncé officially partnered with the service in 2015. Beyoncé announced that she was once again participating in the 22-day challenge before her acclaimed Coachella performance in 2018.

The Greenprint contest closes 22 April at midnight and is open to US citizens over the age of 18.