Fonbnk — Farmer Payouts

Fonbnk handles all outbound USDC → UGX → MTN Mobile Money payments to farmers. It uses a merchant balance model: we deposit USDC to Fonbnk’s Celo address, they credit our merchant balance, then we trigger disbursements via their API.

Architecture

Mantle (protocol settlement)
        ↓
CCIP bridge (quarterly batch, ~$5–10/msg)
        ↓
Fonbnk Celo USDC deposit address
        ↓
Fonbnk Merchant Balance (USD)
        ↓
POST /api/v2/order → MTN MoMo to farmer

There are no Celo contracts or wallets on our side. Fonbnk holds deposited USDC in custody and credits our merchant balance 1:1.

Supported Chains

Fonbnk supports 14 chains for USDC deposits, including CELO_USDC — the one we use:

ARBITRUM · AVALANCHE · BASE · BNB · CELO · ETHEREUM · LISK · OPTIMISM · POLYGON · SOLANA · STELLAR · TON · TRON · XRP

Payment Flow

BatchToken confirmed on Mantle → settlement triggered
        ↓
AsiliChain API → POST /api/v2/order
{
  "paymentChannels": {
    "deposit": { "channel": "merchant_balance", "currencyType": "merchant_balance", "currencyCode": "USD" },
    "payout": { "channel": "mobile_money", "currencyType": "fiat", "currencyCode": "UGX" }
  },
  "recipient": { "phone": "+256...", "name": "Farmer Name" }
}
        ↓
Fonbnk: USD → UGX at live rate
        ↓
MTN MoMo notification to farmer
        ↓
Webhook: order.settled → AsiliChain API
Status: PAYMENT_CONFIRMED

Total elapsed: < 60 seconds

Pre-Launch Setup

Sandbox Testing

Register at sandbox-dashboard.fonbnk.com to:

1. Create a merchant account
2. Get Client ID + API Secret
3. Get your Celo USDC deposit address
4. Configure webhook URL

Basic KYC (under $100 order limit) is sufficient for sandbox testing.

Mainnet Onboarding

1. Full KYB completed
2. Merchant balance funded via Celo USDC deposit
3. IP whitelist configured with your API server IP
4. Webhook URL /api/webhooks/fonbnk registered

Merchant Balance Funding

Maintain a pre-funded pool on Fonbnk’s merchant balance. At Phase 1 scale (~50 farmers):

Item	Value
Average loan	$500
Batch size	$25,000
CCIP bridge cost	~$10/quarter
Pre-fund	$30,000 (50 farmers x $500 + 20% buffer)

Top up quarterly via the CCIP bridge script. Do not bridge per-transaction — batch economics are far better.

Fonbnk vs. Alternatives

Factor	Fonbnk	Yellow Card	Kotani Pay
Uganda MoMo	✅	✅	✅
Celo USDC deposit	✅	❌	❌
Base deposit	✅	❌	N/A
Mantle deposit	❌	❌	❌
Published pricing	N/A	~1% (lowest confirmed)	Not public
Merchant balance	✅	✅	Pool-pull model
Sandbox	✅	✅	Quote-based only
Africa countries	16	~20	~8

Fonbnk chosen because it supports Celo USDC deposits (aligns with Celo Foundation grants), uses a simple merchant balance model (no contracts needed), and has a self-serve sandbox for testing.