diff --git a/lib/opentelemetry/trace/exporter/otlp.lua b/lib/opentelemetry/trace/exporter/otlp.lua
index 68cac86..fe3b0a0 100644
--- a/lib/opentelemetry/trace/exporter/otlp.lua
+++ b/lib/opentelemetry/trace/exporter/otlp.lua
@@ -74,7 +74,7 @@ local function call_collector(exporter, pb_encoded_body)
     return false, res_error or "unknown"
 end
 
-function _M.export_spans(self, spans)
+function _M.encode_spans(self, spans)
     assert(spans[1])
 
     local body = {
@@ -96,12 +96,57 @@ function _M.export_spans(self, spans)
             }
         }
     }
+    local tracers = {}
+    local providers = {}
+    tracers[spans[1].tracer] = 1
+    providers[spans[1].tracer.provider] = 1
     for _, span in ipairs(spans) do
+        local rs_idx = providers[span.tracer.provider]
+        local ils_idx = tracers[span.tracer]
+        if not rs_idx then
+            rs_idx = #body.resource_spans + 1
+            ils_idx = 1
+            providers[span.tracer.provider] = rs_idx
+            tracers[span.tracer] = ils_idx
+            table.insert(
+                body.resource_spans,
+                {
+                    resource = {
+                        attributes = span.tracer.provider.resource.attrs,
+                        dropped_attributes_count = 0,
+                    },
+                    instrumentation_library_spans = {
+                        {
+                            instrumentation_library = {
+                                name = span.tracer.il.name,
+                                version = span.tracer.il.version,
+                            },
+                            spans = {}
+                        },
+                    },
+                })
+        elseif not ils_idx then
+            ils_idx = #body.resource_spans[rs_idx].instrumentation_library_spans + 1
+            tracers[span.tracer] = ils_idx
+            table.insert(
+                body.resource_spans[rs_idx].instrumentation_library_spans,
+                {
+                    instrumentation_library = {
+                        name = span.tracer.il.name,
+                        version = span.tracer.il.version,
+                    },
+                    spans = {}
+                })
+        end
         table.insert(
-            body.resource_spans[1].instrumentation_library_spans[1].spans,
+            body.resource_spans[rs_idx].instrumentation_library_spans[ils_idx].spans,
             encoder.for_otlp(span))
     end
-    return call_collector(self, pb.encode(body))
+    return body
+end
+
+function _M.export_spans(self, spans)
+    return call_collector(self, pb.encode(self:encode_spans(spans)))
 end
 
 function _M.shutdown(self)
diff --git a/spec/trace/exporter/otlp_spec.lua b/spec/trace/exporter/otlp_spec.lua
index 7b2f500..20ed8d6 100644
--- a/spec/trace/exporter/otlp_spec.lua
+++ b/spec/trace/exporter/otlp_spec.lua
@@ -2,8 +2,85 @@ local exporter = require "opentelemetry.trace.exporter.otlp"
 local client = require "opentelemetry.trace.exporter.http_client"
 local context = require "opentelemetry.context"
 local tp = Global.get_tracer_provider()
+local tracer_provider_new = require("opentelemetry.trace.tracer_provider").new
 local tracer = tp:tracer("test")
 
+describe("encode_spans", function()
+    it("one resource span and one ils for one span", function()
+        local span
+        local ctx = context.new()
+        ctx, span = tracer:start(ctx, "test span")
+        span:finish()
+        local cb = exporter.new(nil)
+        local encoded = cb:encode_spans({span, other_spans})
+        -- One resource, one il, one span
+        assert(#encoded.resource_spans == 1)
+        local resource = encoded.resource_spans[1]
+        assert(#resource.instrumentation_library_spans == 1)
+        assert(#resource.instrumentation_library_spans[1].spans == 1)
+    end)
+
+    it("one resource span and one ils for multiple span same tracer", function()
+        local span
+        local ctx = context.new()
+        local spans = {}
+        for i=10,1,-1 do
+            ctx, span = tracer:start(ctx, "test span" .. i)
+            span:finish()
+            table.insert(spans, span)
+        end
+        local cb = exporter.new(nil)
+        local encoded = cb:encode_spans(spans)
+        -- One resource, one il, 10 spans
+        assert(#encoded.resource_spans == 1)
+        local resource = encoded.resource_spans[1]
+        assert(#resource.instrumentation_library_spans == 1)
+        assert(#resource.instrumentation_library_spans[1].spans == 10)
+    end)
+
+    it("one resource span and two ils for spans from distinct tracers", function()
+        local span
+        local ctx = context.new()
+        local spans = {}
+        ctx, span = tracer:start(ctx, "test span")
+        span:finish()
+        table.insert(spans, span)
+        local other_tracer = tp:tracer("exam")
+        ctx, other_span = other_tracer:start(ctx, "exam span")
+        table.insert(spans, other_span)
+        local cb = exporter.new(nil)
+        local encoded = cb:encode_spans(spans)
+        -- One resource, two il, 1 span each
+        assert(#encoded.resource_spans == 1)
+        local resource = encoded.resource_spans[1]
+        assert(#resource.instrumentation_library_spans == 2)
+        assert(#resource.instrumentation_library_spans[1].spans == 1)
+        assert(#resource.instrumentation_library_spans[2].spans == 1)
+    end)
+    it("distinct trace providers provide distinct resources", function()
+        local span
+        local ctx = context.new()
+        local spans = {}
+        ctx, span = tracer:start(ctx, "test span")
+        span:finish()
+        table.insert(spans, span)
+        local op = tracer_provider_new(nil, nil)
+        local other_tracer = op:tracer("exam")
+        ctx, other_span = other_tracer:start(ctx, "exam span")
+        table.insert(spans, other_span)
+        local cb = exporter.new(nil)
+        local encoded = cb:encode_spans(spans)
+        -- two resources with one il, 1 span each
+        assert(#encoded.resource_spans == 2)
+        local resource = encoded.resource_spans[1]
+        assert(#resource.instrumentation_library_spans == 1)
+        assert(#resource.instrumentation_library_spans[1].spans == 1)
+        resource = encoded.resource_spans[2]
+        assert(#resource.instrumentation_library_spans == 1)
+        assert(#resource.instrumentation_library_spans[1].spans == 1)
+    end)
+end)
+
 describe("export_spans", function()
     it("invokes do_request when there are no failures", function()
         local span