Can we generate shadow effect using SAO pass?

I need some guidance how we can generate shadow effect using SAO pass on a plane, If I am using effect composer it covers all my scene I need it only shows shadow on a plane of a object.

composer = new EffectComposer( renderer );
	    composer.addPass(new RenderPass(scene,camera));

            const effectPass = new EffectPass(camera, new POSTPROCESSING.BloomEffect())
            renderPass = new RenderPass( scene, camera );
			composer.addPass( renderPass );
			saoPass = new SAOPass( scene, camera, false, true );
			saoPass.renderToScreen = true;
            saoPass['saoIntensity'] = 0.8;
            composer.addPass( saoPass );

and if I use composer.render() in a render function it gives me undefined error in console and I need to generate AO on plane only, and I need Beauty + SAO effect Thanks for your time