Citrea Bitcoin ZK Rollup Mainnet Launch Reignites Block Space Debate

**Bitcoin ZK-Rollup Project Citrea Launches Mainnet, Unveils BTC-Backed DeFi & Native Stablecoin** On January 29, Citrea—a Bitcoin ZK-rollup project backed by Founders Fund and Galaxy Ventures—officially went live on mainnet. The launch introduces BTC-collateralized DeFi lending, structured products, and its native stablecoin ctUSD, aiming to integrate "idle BTC" into a full DeFi and payment ecosystem. Citrea projects initial active DeFi liquidity on the mainnet will hit $50 million. Issued by MoonPay, ctUSD is pegged 1:1 to cash and short-term U.S. Treasuries. Unlike cross-chain assets, it’s native to Citrea, which mitigates bridge risks and avoids liquidity fragmentation. The project has rekindled a long-running debate: As Bitcoin’s block subsidies decline, should miners’ fee revenue be bolstered via non-payment use cases like DeFi and stablecoins? Proponents argue these use cases represent a sustainable demand source, while critics stress Bitcoin’s block space should prioritize simple, censorship-resistant payments. Notably, during Citrea’s testnet phase, its data availability usage briefly made up nearly 10% of Bitcoin’s monthly data bandwidth—suggesting rollups could have a significant impact on Bitcoin’s block space.